Global estimates of top-five causes of death for school-age children and adolescents, by sex and age group, 2016

# Fig. 2.
Global estimates of top-five causes of YLD for school-age children and adolescents, by sex and age group, 2016  Steps in setting intervention priorities for national SHS

# Tables, figures and boxes
Schools are essential for young people to acquire knowledge, socioemotional skills including selfregulation and resilience, and critical thinking skills that provide the foundation for a healthy future. Access to education and safe and supportive school environments have been linked to better health outcomes. In turn, good health is linked to reduced drop-out rates and greater educational attainment, educational performance, employment and productivity.
WHO has long recognized the link between health and education and the potential for schools to play a central role in safeguarding student health and well-being. In 1995, WHO launched the Global School Health Initiative, which aimed to strengthen approaches to health promotion in schools. Among those approaches, pairing children with health services occupies an important place.
Many health conditions can be better managed or prevented if detected early. The school environment and school health services provide an opportunity for timely interventions across a range of conditions, including anxiety and depression, behavioural disorders, diabetes, overweight, obesity and undernutrition.
There are many reasons why school health services are uniquely placed to contribute to the health and well-being of school-age children. First, they operate where most children are, and they have access to families. Secondly, they are free at the point of use and overcome barriers such as transport issues, limited community services, and inconvenient location or appointment systems, and therefore have the potential to better serve underprivileged populations.
And thirdly, they can have a positive effect on multiple determinants of health and are highly valued by students, parents and communities. But despite all these advantages, school health services have long been overlooked and have not received the deserved attention by researchers, policy-makers and development partners.
This first WHO guideline on school health services helps to fill that gap, with a strong recommendation for the implementation of comprehensive school health services. This recommendation comes at a unique time in history, when COVID-19 has put so sharply in the spotlight the vital link between health and education. While we are still learning the full extent of the health effects of mass school closures, we know that they have resulted in anxiety, depression and mental distress, inability to access the usual points of care, disruption to physical activity and routine, increased child maltreatment and exposure to the dangers of the unregulated digital environment. These problems are not unique to COVID-19 -the pandemic has only exacerbated problems that already existed. This makes it all the more important that adequately resourced and well implemented school health services are in place to provide a safety net for children.
I hope that this WHO guideline on school health services will contribute to the creation of a common language around school health services, will promote evidence-based care through its menu of interventions, will strengthen school nursing and school health professions around the world, and ultimately will improve the health of children. The evidence suggests that if school health services are implemented well, they will have lasting benefits for students.

# Tedros Adhanom Director-General, World Health Organization
Health promotion: the process of enabling individuals to increase control over, and to improve, their health. It moves beyond a focus on individual behaviour towards a wide range of social and environmental interventions. Health promotion can happen formally or informally, in a group or one-on-one and in a clinical setting or at a broader level (including social mobilization and advocacy).
Health worker: a person whose main function is to deliver health promotion, prevention, care and/or treatment services, such as a nurse or clinical psychologist, but not a teacher.
Health-promoting school (HPS): a school that constantly is strengthening its capacity as a healthy setting for living, learning and working. The WHO HPS framework is a holistic, whole-school and comprehensive approach to health promotion that capitalizes on the organizational potential of schools to foster the physical, social and psychological conditions for health. As part of a health-promoting education system, a HPS is described by eight global standards: government policies and resources, school policies and resources, school governance and leadership, school and community partnerships, school curriculum, school social-emotional environment, school physical environment, and school health services (3). Importantly, staff delivering on some of these standards may overlap; for instance, a health worker may support a teacher who is teaching a health education curriculum.
Important outcomes: outcomes that should be taken into consideration during the GRADE process, but are not critical for decision-making and recommendation formulation (1,2). Also see "Critical outcomes".
Intervention: a combination of health service programme elements or strategies designed to assess, improve, maintain, promote or modify health, functioning or health conditions.

# Glossary xiii

# SHS interventions that the GDG categorized as:
Essential everywhere: should be included in SHS everywhere.
Suitable everywhere: are appropriate, but not essential, in SHS everywhere.
Essential/suitable in certain areas: are essential and/or appropriate in SHS in certain geographic areas only.
are not appropriate for inclusion in SHS (inclusion in other types of health service may be appropriate).
Mental health counselling: evidence-based psychological interventions such as cognitive behavioural therapy, problem-solving approaches or motivational interviewing. Also see "Health counselling".
Positive development: healthy transitions and growth in childhood and adolescence, including healthy physical, sexual, cognitive and psychosocial development (4).
Preventive intervention: a health intervention to prevent illness, disease or injury. Preventive interventions can include screening, check-ups and health counselling to prevent health problems.
Procedure or activity (PA): a specific course of action taken as part of a broader health service intervention. Also see "Intervention".
School health services: services provided by a health worker to students enrolled in primary or secondary education, either within school premises or in a health service situated outside the school premises that has an official agreement with the school to provide health services to the school's students.

# School health services
Coverage: is the proportion of a student population that needs SHS and obtains them in a timely manner and at a level of quality necessary to have the desired effect and potential health gains (5).
Equity: is the absence of avoidable, unfair or remediable differences within a student population. It implies that all students should have a fair opportunity to use SHS and no one is disadvantaged from doing so. More broadly, SHS may promote health equity by enabling disadvantaged students to receive health care they may not otherwise receive (6).
Quality: is the degree to which SHS increase the likelihood of desired student health outcomes and are consistent with current professional knowledge (7).
School-linked SHS: SHS that are provided outside of school premises by facilities and/or providers who have a formal agreement with the school administration to provide health services to their students/learners.
Screening: medical tests to check for diseases and health conditions before there are any signs or symptoms, followed by care or referral, as appropriate. Often this refers to universal screening or routine enquiry, that is, asking all patients in all health-care encounters.
Support: provision of supportive care following the guidance of another health service, such as a student's personal doctor or specialist. For example, in this capacity a school health worker would not take primary responsibility for case management, but might administer or supervise the taking of medications, change wound dressings or provide supportive counselling.
Universal health coverage (UHC): all individuals and communities receive the health services they need without suffering financial hardship. UHC includes the full spectrum of essential quality health services, from health promotion to prevention, treatment, rehabilitation and palliative care (6).
WHO source: within this guideline, WHO source is defined as whether and how a health service intervention, procedure or activity for 5-19-year-olds is supported by a global WHO publication. This support or approval may be general, not specifically specified for SHS.

# If an intervention has a WHO source of:
Full GRC support: all aspects of the intervention are supported by a GRC-approved guideline.
Partial GRC support: some -but not all -aspects of the intervention are supported by a GRC-approved guideline. (In addition, some or all aspects of the intervention may be supported by "other WHO" publications.)
Other WHO support: some or all aspects of the intervention are supported by other (not GRC-approved) global WHO publications.
No WHO source identified: no supporting procedures or activities have been found in global WHO publications; or a GRCapproved recommendation specifically states that the intervention should not be done.
This recommendation is based on evidence and a decision-making process that are outlined below and in greater detail in the main text of the guideline and its accompanying Web Annexes A-H.

# Executive summary
Comprehensive school health services should be implemented.
Strength of recommendation: strong.
Certainty of evidence: moderate.
Rationale: this recommendation is strong because:
- all evidence consistently points in a beneficial direction, including evidence related to acceptability and equity;
- the evidence suggests that -if school health services are implemented well -they will have lasting benefits for students;
- the overall certainty of the evidence in the systematic reviews is moderate;
- although there were no studies in low-and middle-income countries that provided highcertainty evidence, the observational studies that took place in low-and middle-income countries also identified benefits and did not identify significant harms; and
- schools offer a compelling, broad and relatively convenient opportunity to reach children and adolescents with needed comprehensive health services.

# Implementation considerations
- This recommendation is for comprehensive school health services that have adequate resources and are implemented well.
- School health services need to be implemented with quality, fidelity and over the long term.
The resource implications must be carefully identified, examined and met.
- In practice, implementation will be variable.
In some settings it may be difficult and/or not yet feasible to implement comprehensive school health services similar to those that the systematic reviews found were evaluated in controlled studies in high-income countries. Substantial resources, time and leadership may be needed to achieve this. In many low-and middle-income countries it may nonetheless be feasible to implement some aspects of comprehensive school health services now, even if not yet all aspects.
- Protecting student confidentiality is paramount, and school health workers are also obliged to prevent possible discrimination or stigma towards students.
School health services (SHS), as defined in this guideline, are services provided by a health worker to students enrolled in primary or secondary education, either within school premises or in a health service situated outside the school. Most countries have some form of SHS, but many such programmes currently are not evidence-based, are not implemented well, are underfunded and/or are delivered with limited reach and scope (8). In all WHO regions, school-age children and adolescents (those aged 5-19 years) experience a range of largely preventable health problems, including unintentional injury, interpersonal violence, sexual and reproductive health issues, communicable diseases, noncommunicable diseases and mental health issues. In addition, school-age children and adolescents have positive physical, sexual, psychosocial and neurocognitive health and development needs as they progress from childhood to adulthood. The need for quality health care for 5-19-year-olds is great, but globally the quality of health services for them are variable and coverage is limited. Schools offer a unique opportunity to implement effective health services at scale for children and adolescents.
Health-promoting schools (HPS) promote health through six pillars: a school's policies, physical environment (including school feeding/ meals programmes), social environment, health curriculum, involvement with the community and health services. In 1995, WHO launched the Global School Health Initiative, which has a goal to improve child, adolescent and community health through HPS. HPS have been found to be effective in improving several aspects of student health
This guideline was developed according to WHO standard procedures (2). An independent external Guideline Development Group (GDG), comprising geographically dispersed and gender-balanced representatives across different sectors, led the formulation of the recommendation and menu of interventions, with the support of an internal WHO and UNESCO Steering Group (see the Annex).
Given SHS consist of diverse possible combinations of services -and this guideline is one of the first global guidance documents to address SHS -only one overarching recommendation is provided; it addresses Key Questions 1 and 2. In addition, to address Key Question 3, this guideline provides practical information on many specific interventions that can be considered for implementation within comprehensive SHS. Importantly, these interventions have not been evaluated through the standard process used to identify recommendations for WHO guideline inclusion. Instead, the specific interventions were assessed through an innovative process involving a review of global WHO guidance documents, an expert survey of intervention priorities and GDG categorization of interventions. These different methodologies are summarized below. Substantial background information and evidence is provided for each intervention, but they are not formal guideline recommendations.
To assess SHS effectiveness and acceptability (Key Questions 1 and 2), a series of research exercises were conducted that built upon each other, as follows.
- A systematic overview of systematic reviews of the effectiveness of comprehensive SHS (Web Annex C).
- Systematic reviews of the (1) effectiveness and (2) acceptability of comprehensive SHS (Web Annex D). These systematic reviews screened the titles and abstracts of 8966 records for potential eligibility, after which 443 full-text articles were assessed for eligibility. In total, 18 high-quality controlled studies were eligible and included in the review. Because all of these were from high-income countries (HIC), the review also included 19 supplementary observational studies in low-and middle-income countries (LMIC).

# Evidence synthesis through a Grading of
Recommendations Assessment, Development and Evaluation (GRADE) process (Web Annex F), including generation of evidence summaries and profiles.

# Results: recommendation Results: menu of interventions
Eighteen controlled studies in HIC were the main evidence source for the systematic reviews. Such sources will have only limited applicability to LMIC, so an additional 19 observational studies from LMIC (11 quantitative and eight qualitative) were included. These 37 studies provided the evidence for the following recommendation.
Comprehensive school health services should be implemented in schools.
This is a strong recommendation, based on moderate certainty of evidence.
The operational definition of "comprehensive SHS" in this guideline is SHS that address at least four -but ideally all -health areas relevant to their student population: positive health and development; unintentional injury; violence; sexual and reproductive health, including HIV; communicable disease; noncommunicable disease, sensory functions, physical disability, oral health, nutrition and physical activity; and mental health, substance use and self-harm.
When developing this recommendation, the GDG highlighted that higher-quality studies, such as randomized controlled trials or non-randomized controlled studies of SHS effectiveness and acceptability, should be a future research priority in LMIC.  Global progress in reducing the non-fatal disease burden has also been limited. Estimated years lived with disability (YLD) -a measure that aims to capture the amount of time lived in states of less than good health -show that skin diseases, irondeficiency anaemia, anxiety disorders and childhood behavioural disorders are top-five causes of YLD among most subgroups (Fig. 2). Some conditions, however, are top-five causes of YLD among certain subpopulations only, such as congenital anomalies and uncorrected refractive errors among 5-9-yearold girls, asthma among 5-9-year-old girls and boys, migraines among 10-19-year-old girls and 15-19-year-old boys, autism and Asperger syndrome among 5-14-year-old boys and depressive disorders among 15-19-year-olds of both sexes. Unlike mortality, where 15-19-year-old boys and young men experience the highest death rates, YLD rates are particularly high for 15-19-year-old girls and young women.
Importantly, where conditions are not seen in Fig. 1 and 2 for a specific subpopulation of children and adolescents, it does not mean that that condition does not cause YLD or death in large numbers or at high rates among that subpopulation, but simply that it is not among the subpopulation's top-five causes of YLD or of death. Note: data are organized from the overall highest to lowest causes of death rates (total for all sexes/age groups), for the top-five causes within each sex/age group. For example, at a rate of 60.0 deaths per 100 000 population, road injury is the highest cause of death rates for all school-aged children (5-19 years); in contrast, meningitis and tuberculosis both have rates of 4.8 deaths per 100 000 population and as such are the lowest among the 11 causes shown.  Note: (a) YLD are an estimate of the burden of disease due to disability; they are calculated by multiplying the incidence of a disorder by its duration and a weight factor that reflects the severity of the disability it causes on a scale from 0 (perfect health) to 1 (dead) to estimate the short-or long-term loss of health associated with that disability. (b) Data are organized from the highest to lowest causes of rates of YLD overall (total for all sexes/age groups), for the top-five causes within each sex/age group. For example, at a rate of 3718 YLD per 100 000 population, iron-deficiency anaemia is the highest cause of YLD for all school-aged children (5-19 years). In contrast, at a rate of 196 YLD per 100 000 population, uncorrected refractive errors (top of one column) are the lowest among the 10 causes shown.

# Source: WHO (14).

# Causes of death

# Source: WHO (14).

# Causes of YLD for school-aged children (5-19 years)

# SHS in the context of school health and HPS
Schools have an extraordinary potential to provide intensive, long-term and large-scale health programmes to children and adolescents (8). Globally, most children and adolescents are enrolled in school, and an increasing proportion of students continue enrolment from primary to secondary school. The global adjusted net primary and secondary school enrolment rates 1 are 89% and 66%, respectively (21-23). A system of SHS therefore may be the only institutional way to meet the health needs of the majority of school-age children and adolescents on an almost daily basis (24). Operating in an educational setting, SHS are well placed to exploit the inextricable link between health and education.
SHS operate in a broader context of school health that was articulated by WHO in 1995 with the launch of the Global School Health Initiative. The Initiative had the goal to improve child, adolescent and community health through multifaceted health programming in schools (25). Further expanded in 2000 through the partnership for Focusing Resources on Effective School Health -a FRESH Start approach (26,27), it supported countries to develop school health programmes and increase the number of HPS, defined as "schools that constantly strengthen their capacities as healthy settings for living, learning and working" (28). Importantly, effectively addressing child and adolescent health needs in a HPS requires evidence-based interventions that directly target health and well-being, as well as interventions that focus on the structural and intermediary social determinants of health and well-being (29). HPS initiatives have been shown to be capable of improving health-related behaviours, such as physical activity, physical fitness, fruit and vegetable intake, preventing tobacco use and preventing bullying (9). Interventions delivered through schools, including deworming, insecticidetreated bed net promotion, tetanus toxoid and human papillomavirus vaccination, oral health promotion, vision screening and provision of spectacles, micronutrient supplementation, multifortified foods and school feeding interventions, offer excellent cost-effectiveness and very high benefit-cost ratios (30). Investments in the health and education of adolescents generate economic and social benefits ranging from 6-to 12-fold returns on investment (31).
Increasing access to comprehensive SHS is one of the new eight global standards for HPS. While HPS have been found to be effective, establishing them with high coverage, quality, equity and sustainability has proved challenging in many countries (9,32), mainly due to poor integration of health and health promotion into education systems (10). In 2017, the Global Accelerated Action for the Health of Adolescents (AA-HA!) Guidance recognized this gap and called for school health programmes to be prioritized as an important step towards universal health coverage (UHC), urging that, "Every school should be a health promoting school" (4). To support this goal, in 2018 WHO and UNESCO launched the "Making Every School a Health Promoting School" initiative (10), in collaboration with other United Nations entities, such as the United Nations Children's Fund (UNICEF) and the United Nations Population Fund (UNFPA). As part of the initiative, global standards and implementation guidance for HPS have been developed (3,33). The eight global standards relate to one another to comprise a HPS system that recognizes the important role of SHS (Fig. 3).

# Government policies and resources
The whole of government is committed to and invests in making every school a HPS

# School curriculum
The school curriculum supports physical, social-emotional and psychological aspects of student health and well-being

# School policies and resources
The school is committed to, and invests in, a wholeschool approach to being a HPS

# School socialemotional environment
The school has a safe, supportive socialemotional environment

# School governance and leadership
A whole-school model of school governance and leadership supports a HPS

# School physical environment
The school has a healthy, safe, secure, inclusive physical environment

# School and community partnerships
The school is engaged and collaborates with the local community for HPS

# School health services
All students have access to comprehensive schoolbased or school-linked health services that meet their physical, emotional, psychosocial and educational healthcare needs
The eight global standards for HPS, are intended to function as a system (Fig. 3 and Table 1). The standards are intentionally aspirational, looking towards progressive realization of a vision for healthy schools. Introduction

# The need for guidance on SHS
While the FRESH partnership and other partners produced clear, evidence-based guidance for some components of HPS (34-37), guidance on SHS is scarce (38)(39)(40)(41)(42)(43). It is important therefore that the global standard on SHS is reinforced by a guideline supported by a rigorous review of the literature and implementation experience. Global and regional overviews of SHS have shown that while most countries have some form of SHS, many such programmes are not evidence-based, are not implemented well, are underfunded and/or are delivered with limited reach and scope (8,44). SHS are often omitted in national whole-school programmes (Box 1, Web Annex B).

# BOX 1. Key highlights from global reviews of national SHS programmes
- School-based or school-linked health services exist in at least 102 countries (8). Most commonly, they provide vaccinations, sexual and reproductive health education, vision screening, nutrition screening and nutrition education. Important interventions, including the provision of mental health services and injury and violence prevention interventions, are not given sufficient consideration in routine SHS provision.
- Typically, SHS are provided within school premises by dedicated school health personnel (8).
- Most commonly reported challenges that SHS face include staff shortages, high workloads, lack of training and continuing professional education opportunities, and low motivation of school health personnel. In addition, inadequate coordination among multiple service providers or sectors (in particular, health and education) is reported frequently, as well as inadequate financing and quality of care issues (8).
- Even when national SHS frameworks reiterate a whole-school approach to health, they sometimes marginalize or omit the SHS component (Web Annex B).
- The extent of SHS programmes in countries may vary from minimal, teacher-delivered interventions, to occasional visits by a health worker (usually a nurse, sometimes a medical officer), to a fairly comprehensive SHS programme provided with high coverage by nurses based either full-or part-time in schools or by a team of health workers in school-based health centres (Web Annex B).
- Despite recognition of the importance of collaboration between the education and health sectors, the fundamentally intersectoral nature of SHS poses challenges. An analysis of case studies from eight countries -Australia, Bangladesh, Egypt, the Lao People's Democratic Republic, Rwanda, South Africa, Turkey and the United States of America -found that in practice the implementation of SHS fell to one lead sector (education or health).
In settings where SHS essentially were only led and implemented by the education sector, SHS interventions were extremely limited and typically were carried out by lay people without clinical training (Web Annex B).

# Objective and scope of the WHO guideline on SHS
The objective of this guideline is to provide national governments and other stakeholders with detailed guidance on the effectiveness, acceptability and content of SHS involving a health worker.
The guideline is intended to support national governments and national and international partners in their efforts to develop effective, evidence-informed SHS programmes to better meet the health and development needs of school-age children and adolescents.
The scope of this guideline is services provided by a health worker to students enrolled in primary or secondary education, either within school premises or in a health service situated outside the school. Specifically, this guideline provides:

# Target audience of the WHO guideline on SHS
The primary target audience for the WHO guideline on SHS is government policy-makers and programme managers and private (for-profit and not-for-profit) stakeholders in the health and education sectors responsible for the health and well-being of 5-19-year-old students attending schools or similar educational establishments. Introduction

# BOX 2. Key terms in this guideline
A health worker is a person whose main function is to deliver health promotion, prevention, care and/or treatment services, such as a nurse or clinical psychologist, but not a teacher.
SHS are provided by a health worker to students enrolled in primary or secondary education, either within school premises or in a health service situated outside the school premises that has an official agreement with the school to provide health services to the school's students. The guideline does not address other aspects of HPS that do not involve a health worker, such as health education provided by a teacher in class. Importantly, it also does not suggest a one-sizefits-all approach to SHS. It broadly is applicable to different delivery systems, such as school-based versus school-linked, or using a team of differently trained health workers versus a single cadre of health worker. It does not, however, provide specific recommendations about the content or delivery of SHS, as this will depend on the context and resources available, including the broader health system and existing services.
The guideline is expected to be part of a series of detailed global guidance documents on school health, including SHS programming and implementation. More broadly, it is hoped that it will help achieve specific SDG targets, including, but not limited to:
- ending the epidemics of AIDS, tuberculosis, malaria and neglected tropical diseases; combatting hepatitis, waterborne diseases and other communicable diseases; reducing premature mortality from noncommunicable diseases through prevention, treatment and promotion of mental health and well-being; strengthening the prevention and treatment of substance abuse; and achieving UHC (SDG 3); and
- eliminating all forms of violence against women and girls (such as sexual exploitation); eliminating all harmful practices (including child, early and forced marriage and female genital mutilation); and ensuring universal access to sexual and reproductive health and reproductive rights (SDG 5).
Box 2 shows key terms as defined in this guideline; further explanation and definitions are provided in the glossary.

# Guideline development process

# Governance and management structures 2.2 Declarations of interest and management of conflicts of interest

# Collaboration with external partners
A Steering Group was established to provide overall technical support to the guideline development process. The group was led by the WHO Department of Maternal, Newborn, Child and Adolescent Health and Ageing, with representatives from other relevant WHO departments and programmes, the six WHO regional offices and UNESCO. The Steering Group proposed experts with technical knowledge related to school health and expertise in evidence review and synthesis to be invited to be part of the GDG.
The GDG was made up of academics, public health professionals and clinicians not working for any United Nations organization who, between them, had multidisciplinary expertise in school health, adolescent health and child health. Consideration
To comply with WHO's Conflict of Interest Policy, the Steering Group followed the revised Guidelines for declaration of interests (WHO experts) (45). Declarations of interest (DoI) were requested from:
- all GDG members;
- all experts and external partners involved in the evidence review process;
- all experts and external partners involved in guideline development and drafting; and
- all experts and external partners invited to review evidence profiles and the draft guideline.
A letter requesting completion of a DoI form and submission of a curriculum vitae was sent to all potential GDG members before they were appointed.
The Stigma and Resilience Among Vulnerable Youth Centre at the University of British Columbia, Canada, supported the development of the guideline by was given to geographic diversity and gender balance. A Chair of the GDG was appointed from within the membership of the GDG to facilitate and guide the discussions of members, clarify their viewpoints and summarize issues that emerged from discussion.
Two external experts independently reviewed the guideline proposal before it was submitted to the WHO GRC. An External Review Group of five members was appointed to provide peer review of the content of the draft guideline.
The Annex lists all members of the GDG and the External Review Group, with gender, nationality and/or country of residence and institutional affiliation.
They were asked to agree to the publication of a summary of declarations in the guideline. Once received, the Steering Group reviewed the DoI forms and additional information (such as Internet and bibliographic database searches) and evaluated if there were any conflicts of interest. No significant conflicts were identified, so no further action was required. At each meeting, members of the GDG were given the opportunity to update or amend their declaration. Any member of the GDG was free to comment or express concern about declared interests of another group member. No significant conflicts were identified throughout the process (see the Annex).
administering the survey of expert opinion and conducting preliminary analysis of the survey data.

# Managing group processes and decision-making
Three GDG meetings were held during the guideline development and decision-making processes. There were two in-person meetings in Geneva, Switzerland, in May and October 2019, and one global virtual meeting in April 2020. Originally, the third meeting was also planned to be in-person, but after the onset of the COVID-19 pandemic it was instead held as a series of three two-hour virtual sessions for both western and eastern hemisphere subgroups. It was necessary to hold subgroup sessions separately to accommodate different time zones around the world. GDG members and Steering Committee members selected which subgroup they wished to join and then participated only in the meetings of that subgroup. Only the GDG Chair, the GRADE Methodologist and two WHO Secretariat members attended all subgroup sessions.
All members of the GDG, the External Review Group and the evidence-review and synthesis teams were asked to complete and sign the standard Prior to each of the three GDG meetings, members received detailed background documents for review. This information was also summarized in presentations during each meeting prior to the GDG Chair and/or the GRADE Methodologist facilitating the GDG's discussion and decision-making. During the third meeting, the GDG Chair only substantively contributed to discussions, and voted, within the sessions of Subgroup 1. Consensus was considered to be agreement among the members of the GDG when all members indicated their support for a decision and/or recommendation, including its phrasing. There was a protocol for voting in the event of disagreement, with a 60% majority considered sufficient, but in practice this was not required to decide any of the guideline's Key Questions.
WHO agreement for confidentiality. In addition, GDG members were reminded of the confidentiality requirement at each meeting.

# Key Questions

# Health areas and types of SHS activity
Three Key Questions informed the development of this guideline.
- Key Question 1. Are comprehensive SHS effective in improving health outcomes or in increasing coverage of health services for school-age children and adolescents? This included effectiveness in economic studies (cost-saving, cost-benefit or cost-effectiveness).
- Key Question 2. Are comprehensive SHS acceptable to stakeholders, such as school-age children and adolescents, parents, teachers and policy-makers?
- Key Question 3. What should be the content of comprehensive SHS in different contexts?
Seven broad health areas are defined and used in this guideline (see Chapter 5). These were adapted from the health areas used in the Global Accelerated Action for the Health of Adolescents (AA-HA!) Guidance (4). The seven health areas are:

# Overview of guideline development methodology
This guideline was developed according to WHO standard procedures for developing guidelines (2).
A WHO guideline recommendation is developed through a complex process of systematic review and evidence assessment. Given SHS consist of diverse possible combinations of services -and this guideline is one of the first global guidance documents addressing SHS -only one overarching recommendation is provided; it addresses Key Questions 1 and 2.
In addition, to address Key Question 3, this guideline provides practical information on many specific interventions that can be considered for implementation within comprehensive SHS. Importantly, these interventions have not been evaluated through the standard process used to identify recommendations for WHO guideline inclusion. Instead, the specific interventions were assessed and categorized through an innovative process involving a review of evidence and recommendations in global WHO guidance documents, an expert survey for preliminary categorizations of interventions, and a final SHS GDG categorization of interventions. Substantial background information and evidence is provided for each intervention and its categorization, but they are not formal guideline recommendations.
Fig. 4 provides an overview of the steps taken to answer the three key research questions during guideline development.

# Systematic overview and systematic reviews of the effectiveness and acceptability of comprehensive SHS
The overview and systematic reviews in this section were conducted using the Preferred Reporting Items for Systematic reviews and Meta-analyses (PRISMA) approach (Web Annex D) (46). At its first meeting in May 2019, the GDG considered different methods for synthesizing and evaluating the systematic review evidence. The GDG discussed and agreed to use GRADE, which assesses the certainty or the quality of the body of evidence across studies for each outcome (1,50). The GDG also considered using WHO-INTEGRATe evidence, which is a tool for transparently reporting evidence-todecision frameworks (51). It was decided, however, not to use INTEGRATe at the time when these systematic reviews were being designed, because there was no prior experience of using WHO-INTEGRATe for guideline development.
The initial systematic review search identified 8523 records, after removal of duplicates. The screening and review procedures are summarized in Web Annex D, which also provides a detailed description of the methodology of these systematic reviews of the effectiveness and acceptability of comprehensive SHS.

# Population, intervention and comparator
Table 2 details the population, intervention and comparator for the systematic reviews of the effectiveness and acceptability of comprehensive SHS. Papers were included only if the SHS had been delivered or supervised by a health worker, and excluded if the service was delivered by trained teachers without the involvement of a health worker.
For the purpose of the systematic reviews, as in the guideline, "comprehensive SHS" were defined as those having interventions within at least four health areas (section 3.2 and Chapter 5).

# Measure Characteristics
Population Children (5-9 years) and/or adolescents (10-19 years) enrolled in schools
The intervention must have had the following characteristics:
- school-based or school-linked health services;
- included studies must have investigated the effectiveness of a SHS that includes interventions for at least four health areas (see section 3.2);
- based on the numbering of the seven types of SHS activities used in section 3.2:
-the intervention must have used at least one "clinical" strategy from: (3) screening;

# Effectiveness outcomes
Critical and important outcomes were agreed between the review team and the Steering Group and were endorsed by the GDG, following the definitions given by the WHO GRC, in which critical outcomes are those that are critical when formulating recommendations and important outcomes are those that should also be taken into consideration but are not critical for decision-making (2).
Critical effectiveness outcomes were defined as improvement in outcomes related to shortterm mortality or morbidity that would otherwise require acute major health service expenditure or improvement in key educational metrics. Important effectiveness outcomes were defined as those affecting chronic morbidity, the academic climate or SHS coverage. The specific critical and important effectiveness outcomes that were considered are shown in Table 3.

# Outcomes Characteristics
Critical effectiveness outcomes Outcomes related to short-term mortality or morbidity that would otherwise require acute major health service expenditure or key educational metrics:
- suicide-related outcomes, including ideation, plans, gestures and attempts

# Acceptability outcomes
The specific critical and important outcomes that would be considered in the review were agreed

# Systematic review process
The systematic reviews of effectiveness and acceptability of comprehensive SHS screened the titles and abstracts of 8966 records for potential eligibility, after which 443 full-text articles were assessed for eligibility (Web Annex D). High-quality studies were identified; these were defined a priori as systematic reviews or randomized controlled trials or non-randomized controlled studies. In total, 18 high-quality studies, all of which used a controlled design, were found to be eligible and were included in the review. Because all of these were from HIC, the review also included observational studies conducted in LMIC. This resulted in 19 supplementary observational studies from LMIC.
Data were extracted from all eligible studies and quality assessment was conducted on each included study. For the non-randomized controlled studies and for the cross-sectional studies, quality assessment was conducted using the Risk Of Bias In Non-randomized Studies of Interventions (ROBINS-I) assessments (52). Within the ROBINS-I tool, all controlled studies start with a high level of certainty. Quality of economic studies was assessed using the Critical Skills Appraisal Programme checklist to evaluate the quality of economic evaluations (53).
Because of substantial variation in the different types of interventions covered and in line with WHO guidance (2), the findings of the included studies primarily were synthesized narratively and organized according to the outcomes of interest (54). Where data allowed and studies were considered methodologically similar, data were pooled using fixed-effects meta-analysis to create estimates of effect, including odds ratios (ORs) and 95% confidence intervals (CIs) for dichotomous data and mean differences with standard deviations for continuous data.

# Outcomes Characteristics
Critical acceptability outcome User satisfaction as reported by the child/adolescent Important acceptability outcomes - Access (student had a regular health-care provider to whom they had consistent access)
- Safety and respect
- Health-care worker spent enough time with the student
- Satisfaction from the provider point of view
- Feasibility of implementation from the provider point of view between the review team and the Steering Group and were endorsed by the GDG. These are shown in Table 4.
Certainty in the findings of the studies for each outcome was assessed according to GRADE guidance, which entails assessing the potential for risk of bias, imprecision, inconsistency, indirectness and publication bias for each finding (55). When using the ROBINS-I to assess risk of bias (52), GRADE ratings for the controlled evaluation studies commenced at high certainty and were then downgraded. For example, risk of bias was downgraded once for a response rate below 80% and twice for a response rate under 60%; imprecision was downgraded once for wide CIs or for a sample size below 300 and twice for a sample size below 100 participants; and inconsistency was downgraded once for unexplained heterogeneity between studies indicated by I 2 > 50%. The rating for the observational (cross-sectional) studies started as low and was eligible to be increased for factors strengthening the evidence base, such as consistency over large numbers of studies and participants, dose-response relationship, or if the effect was present despite confounders tending in the opposite direction (56).
The 2014 WHO handbook for guideline development (2) was used to select an overall certainty rating across outcomes. The handbook recommends that if there is higher quality of evidence for one or more critical outcomes and this is sufficient to support a recommendation, there is no reason to downgrade the overall quality of evidence because of lowerquality evidence for another critical outcome that supports the same recommendation.
For the qualitative studies, the GRADE Confidence in the Evidence from Reviews of Qualitative research (GRADE-CERQual) approach was used to determine confidence in the overall findings (57,58).

# Developing the recommendation
Once the systematic review evidence was identified and synthesized and its quality assessed, the GDG, with the support of the Steering Group, followed the GRADE framework in considering specific factors that may affect the recommendation and its strength and direction. Criteria that were considered when moving from evidence to recommendations were: quality or certainty of the evidence, balance of benefits and harms, values and preferences, resource implications, priority of the problem, equity and human rights, and acceptability and feasibility (2,59). Evidence-to-decision tables were generated to help structure and document the GDG discussion by focusing on factors that would influence the direction and strength of the potential recommendation(s).
Generally, strong WHO recommendations are based on moderate-to-high certainty of evidence, depending on the other factors that are taken into consideration, as detailed above (2). Making a strong recommendation based on low or very low certainty of evidence would be unusual and would require special justification (2).

# Development of menu and compendium of interventions

# Survey results
Responses to all of the interventions listed in the questionnaire were generally favourable, with the vast majority of respondents ranking almost all of the 86 interventions somewhere in the range from suitable to essential within SHS.
Several health promotion and education interventions had the highest overall ranking as essential in SHS everywhere, indicating that these were considered to be very important roles for health workers to perform within a school setting, although answer order bias may have contributed to this pattern. The clinical interventions that ranked most highly as essential in SHS everywhere were in the areas of immunization and mass drug administration, screening, assessment and general care. Similarly, among the 378 interventions that respondents wrote in as additional essential interventions for inclusion in SHS, the most common suggestions were in the areas of health education, other aspects of HPS and screening and care for noncommunicable conditions.
Web Annex G describes the methodology and findings from the global survey of expert opinion in more detail.

# GDG prioritization and categorization of interventions
At its October 2019 meeting, the GDG developed a final list of 94 interventions that were categorized for possible inclusion within SHS. Several steps were taken in this process, including the following.

# Design and finalization of the menu and compendium of interventions
The GDG proposed that the 87 essential or suitable interventions be organized in an at-a-glance menu of interventions for national governments to consider when developing or refining SHS in their respective countries. This menu should provide an overview of each intervention's health area, type of health activity, WHO source and final GDG categorization as essential or suitable for inclusion within SHS, by location. Box 3 explains the different categories of "WHO source" as used in this guideline.
The GDG further instructed WHO that the at-aglance menu should be linked to a compendium that lists the WHO sources and details published WHO procedures or activities for each of the 87 interventions that were identified as essential or suitable. Like the menu, this compendium was used for background information while the GDG considered possible SHS categorization of interventions during the guideline development, but was also intended to be a resource for national governments and their partners within the guideline itself.
In November 2019, an additional targeted review of global WHO guiding documents was undertaken to update the February 2019 literature review. This final review clarified the WHO sources of interventions where needed and produced the final list of 531 health service procedures or activities that provide evidence to the menu and compendium of 87 interventions.

# BOX 3. Understanding the WHO sources of interventions
The GDG drew on multiple sources of information when considering how to categorize interventions for inclusion within SHS, including their own expertise and discussion, the survey of experts, and the review of information published for each intervention within global WHO guidance documents. The review of 149 global WHO publications identified 531 health service PAs for 5-19-year-olds. While the GDG reviewed this detailed information during their decision-making, they also requested an overview of it, as follows.
- First, global WHO publications were considered to be approved by the GRC ("GRC-approved") if they detailed the GRC approval process and/ or were included in a list of GRC-approved publications within a WHO compilation.
- Second, an intervention was considered to have:
- "full GRC" support if all aspects of the intervention were supported by a GRCapproved guideline;
- "partial GRC" support if some, but not all, aspects of the intervention were supported by a GRC-approved guideline (in addition, some or all aspects of the intervention may have been supported by "other WHO" publications);
- "other WHO" support if some or all aspects of the intervention were supported by other global WHO publications (that is, those that have not gone through the GRC-approval process); and
- "no WHO source identified" if no supporting procedures or activities had been found in global WHO publications or a GRC-approved recommendation specifically stated that the intervention should not be done.
"WHO source" is a novel form of categorization and is not an evidentiary standard. Recommendations within GRC-approved guidelines may have variable certainty of evidence, so "WHO source" neither indicates the quality nor the strength of the evidence. WHO publications are cited throughout this guideline and its Web Annexes so readers can directly consult them for information about the strength and quality of evidence for specific interventions.
Recommendation, rationale, summary of evidence-to-decision judgements and implementation considerations
Comprehensive school health services should be implemented.
Strength of recommendation: strong.
Certainty of evidence: moderate.
Rationale: this recommendation is strong because:
- all evidence consistently points in a beneficial direction, including evidence related to acceptability and equity;
- the evidence suggests that -if school health services are implemented well -they will have lasting benefits for students;
- the overall certainty of the evidence in the systematic reviews is moderate;
- although there were no studies in LMIC that provided high-certainty evidence, the observational studies that took place in LMIC also identified benefits and did not identify significant harms; and
- schools offer a compelling, broad and relatively convenient opportunity to reach children and adolescents with needed comprehensive health services.
Summary of GDG evidence-to-decision judgements

# Implementation considerations
- This recommendation is for comprehensive SHS that have adequate resources and are implemented well.
- SHS need to be implemented with quality, fidelity and over the long term. The resource implications must be carefully identified, examined and met.
- In practice, implementation will be variable.
In some settings it may be difficult and/or not yet feasible to implement comprehensive SHS similar to those that the systematic reviews found were evaluated in the controlled studies in HIC. Substantial resources, time and leadership may be needed to achieve this. In many LMIC, it may nonetheless be feasible to implement some aspects of comprehensive SHS now, even if not yet all aspects.
- Protecting student confidentiality is paramount, and school health workers are also obliged to prevent possible discrimination or stigma towards students.

# Recommendation, rationale and implementation considerations
The recommendation, rationale, summary of evidence-to-decision judgements and implementation considerations are shown in Box 4.
The GDG found that the research on SHS effectiveness and acceptability has been limited to date (for instance, it has taken place primarily in HIC), so the certainty or quality of evidence is moderate. They considered this moderate certainty of evidence together with other factors -such as the balance of benefits and harms, values and preferences, resource implications, priority of the problem, equity and human rights, acceptability and feasibility -in its judgement of the strength of the evidence (for example, all evidence from HIC and LMIC consistently points in a beneficial direction).
These factors together contributed to the GDG's strong recommendation that comprehensive SHS be implemented. In other words:
- a strong recommendation indicates the GDG's confidence that the desirable effects of comprehensive SHS outweigh possible undesirable consequences; and
- moderate certainty of evidence means that the GDG was moderately confident in the effect estimate -that is, that the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different (2).
Section 4.2 provides a brief summary of the evidence for this recommendation, while section 4.3 provides an overview of the evidence-to-decision process that informed it. Web Annex E provides more detailed evidence summaries from the systematic reviews of effectiveness and acceptability of comprehensive SHS. Web Annex F provides the GRADE evidence profiles and evidence-to-decision tables; note the GRADE tables are included within the evidence-todecision tables.

# Summary of evidence
In total, 18 studies with high-quality research designs were the main evidence source for the systematic reviews. None of the systematic reviews identified in the search directly addressed the review questions, so they were only used to check that the searches had identified all eligible primary studies. No eligible randomized controlled studies were found.
Of the 18 controlled studies, 11 addressed effectiveness, eight addressed economic outcomes and four addressed acceptability (five studies addressed two of these outcomes: effectiveness plus economic (n = 2) or effectiveness plus acceptability (n = 3)).
As all of this evidence was derived from HIC, supplementary data from observational studies in LMIC were also included, which yielded an additional 19 studies (11 quantitative and eight qualitative). Of the 19 observational studies in LMIC, two addressed effectiveness (one quantitative and one qualitative), none addressed economic outcomes and 18 addressed acceptability (one study addressed both effectiveness and acceptability).
The summary of evidence presented to the GDG is given in Web Annex F, Table F.1. This is further described below.

# Critical effectiveness outcomes
From the 11 studies with high-quality, non-randomized controlled research designs that reported on effectiveness outcomes (all of which were conducted in HIC), seven reported on at least one critical effectiveness outcome; the others reported only important outcomes. The studies with nonrandomized controlled research designs that could be assessed using GRADE were all conducted in HIC. Specifically, there was moderate strength of evidence of a benefit of SHS on the critical effectiveness outcomes of emergency department visits for asthma in two studies in the United States of America (total 2762 participants, OR = 0.48 (95% CI: 0.31, 0.73; p = 0.0006); no heterogeneity; I 2 = 0%), with reduced risk of emergency department visits for asthma among students attending schools with, versus those without, comprehensive SHS (60,61). Also, there was very low strength of evidence on school absence/ attendance (three studies in the United States of America with 6664, 3181 and 2305 participants, totalling 12 150, OR = 0.78 (95% CI: 0.69, 0.87; p < 0.0001)) for the risk of absence among students with, versus those without, SHS (substantial heterogeneity; I 2 = 64%) (61)(62)(63). The heterogeneity between the study findings may have been because one included children from pre-kindergarten to eighth grade (up to approximately 14 years) whereas the other covered the age range from 12 to over 18 years.
One observational study of only 31 participants in Turkey provided very low strength of evidence of a benefit of comprehensive SHS on school absence and academic progress (64).

# Critical economic effectiveness outcomes
The eight studies with high-quality, non-randomized controlled research designs that reported on economic outcomes were conducted in HIC. Specifically, seven in the United States of America reported on at least one critical economic outcome, while the eighth, in Japan, reported willingness to pay.
Four studies conducted in the United States of America provided moderate strength of evidence that comprehensive SHS were cost-saving; these studies involved a total of 7704 participants (273, 109, 6664 and 658 respectively) (61,62,65,66).
Three other studies in the United States of America (5056, 1430 and 477 163 participants; total 483 649) showed cost-benefits (67-69).

# Important effectiveness outcomes
From the 11 studies with non-randomized controlled research designs that reported on effectiveness outcomes (all of which were conducted in HIC), five reported on at least one important effectiveness outcome. Of those that could be assessed in GRADE, one study of 1994 participants in the United States of America had a moderate strength of evidence of a benefit of SHS on the important effectiveness outcomes in terms of students who reported that they had carried a weapon (OR 0.68 (0.53 to 0. Other important outcomes from non-randomized controlled studies that could not be assessed using GRADE were relatively low health complaints, and relatively improved quality of life and school engagement (65,71,72).
One very small quantitative observational study from LMIC that involved only 31 participants provided very low strength of evidence of a benefit of comprehensive SHS on quality of life (64).
Regarding the qualitative data from LMIC, using the GRADE-CERQual approach, there was low confidence in the evidence on the existence of policies regarding SHS. One study of 30 health workers found there were no written plans guiding SHS work in the region of the United Republic of Tanzania studied (73).

# Critical acceptability outcomes
All of the studies with non-randomized controlled research designs were conducted in HIC. From those that evaluated the acceptability of comprehensive SHS there was moderate strength of evidence of a benefit of SHS on the critical acceptability outcome of user satisfaction in HIC (74,75).
The observational (cross-sectional) studies from LMIC that evaluated the acceptability of comprehensive SHS were conducted in Egypt and Tunisia (two studies; 1121 and 625 participants; total 1746) (76,77). These studies suggest that users were less satisfied with their SHS than those in HIC, although there was no information about how satisfied they would have been with any realistic alternative or with no SHS. - in the first study, in Iraq, school principals' overall satisfaction was rated as "satisfied to some extent" (82);

# Important acceptability outcomes
- in the second, in Turkey, 337 (93.6%) teachers in private schools and 338 (93.9%) teachers in public schools believed that school nurses were needed (83); and
- in the third, in the Islamic Republic of Iran, the percentage of participants (health trainers, training managers and teachers working in elementary schools) agreeing that standards were met was: 94% for first-aid and screening functions of nurses; 69% for consultations with colleagues, peers and mental health consultants; 72% for health education; 76% for diagnosis; 62% for managing health planning with educational plans; but only 39% for using a suitable evaluation system for the plan for students, parents and staff (84).
A key issue in implementation reported by one observational (cross-sectional) study in an LMIC was lack of competency among primary school nurses regarding sexual health issues (one study in the Republic of Korea with 595 participants) (85).

# Qualitative acceptability findings
In the qualitative studies, there was moderate confidence in the evidence that users were satisfied with SHS. This is based on three studies that ascertained the views of 20 school nurses in South Africa (86), 44 adolescents in Brazil (87) and 21 managers and health professionals in Brazil (88) (total 85). Particular attributes of SHS highlighted were that they were comprehensive, convenient, necessary, and offered an opportunity for gaining information and learning that may be beneficial in maintaining health. In addition, in one of the studies in Brazil, some of the student users perceived them as a "blessing" that inspired their gratitude (87).
The synthesis of the qualitative data from LMIC also showed moderate confidence in the evidence of the feasibility of SHS implementation (seven studies with a total of 157 participants). Four of these took place in Brazil and assessed the views of 15 primary health-care nurses (89), 39 health professionals, teachers and managers (90), 10 teachers (91) and 21 managers and health professionals (87). One study of 30 health workers took place in the United Republic of Tanzania (73), while two studies took place in South Africa, assessing the views of 20 school nurses (86) and 22 health-care providers (92). Potential SHS benefits noted in the seven studies were identifying health problems such as dental, visual and nutritional problems (including obesity), delayed vaccination status and social risk conditions, and integrating health, school and family.

# Evidence-to-decision process
In its April 2020 meeting, the GDG reviewed the findings of the systematic reviews. Where no evidence was available for criteria within the evidence-to-decision tables, this was noted and GDG participants were requested to comment based on their expert opinion. Based on the evidence from the systematic reviews and their own expert opinions, each GDG subgroup made independent judgements about each of the questions, as summarized in Table 5, which also shows the overall direction and main points of the group discussion prior to making judgements. Rationale: the Convention on the Rights of the Child includes the right to the highest attainable standard of health (93).
The SDGs also support this; for example, ensure healthy lives and promote well-being for all at all ages (SDG 3), reduce inequality within and among countries (SDG 10) and build effective, accountable and inclusive institutions at all levels (SDG 16). Moreover, adolescents are recognized as having very high unmet needs for health, including those related to mental health and sexual and reproductive health. Problems that arise during the second decade of life affect later health and development (4,16). In addition to worldwide recognition of child and adolescent health as a priority, individual countries (such as the United States of America) have also stated that it is a national priority to support the health and education of students and have specific priorities, such as reducing suicides among young people.

# How substantial are the benefits? Moderate Moderate
Rationale: the systematic reviews of controlled studies found evidence of a benefit of comprehensive SHS on the critical effectiveness outcomes of reduction in suicide planning (one study; 1 994 participants), hospitalization for asthma (one study; 273 participants), emergency department visits for asthma (five studies; total 17 166); school absence/attendance (three studies; total 12 150); and academic progress (one study; 2 305 participants). Some of these are critical outcomes (such as reduction in suicide planning). The judgement was "Moderate" because some of the benefits were based only on one study and there was little evidence to date based on LMIC experiences. The GDG noted that benefits may vary in LMIC.

# How substantial are the harms? Uncertain Small
Rationale: the reviews considered a wide range of critical and important outcomes that could have gone in either direction of benefit or harm, but there was no evidence of harm. One possible exception was a qualitative study of SHS acceptability in an LMIC in which SHS health workers reported they did not have plans to guide their work. In addition, the lack of evidence of harm may reflect a lack of measuring and/or a lack of reporting of possible harms. Both subgroups discussed making a judgement of "Small", "Trivial" or "Uncertain". Both subgroups acknowledged that an intrinsically sound and beneficial SHS design could potentially become harmful if implemented in inappropriate ways, such as in resource-limited LMIC, but the same could be said for all health services. Subgroup 1 ultimately selected "Uncertain" because some studies did not specifically ask whether there were potential negative outcomes. Subgroup 2 instead selected "Small", while noting that there was uncertainty, particularly as there was little evidence from LMIC.

# Questions related to the health of school-age children and adolescents and/or SHS GDG judgement

# Subgroup 1 Subgroup 2
- What is the overall certainty of the evidence? Moderate Moderate
Rationale: the GRADE tables present some variability. The overall body of evidence ranged from moderate to low certainty of evidence for critical outcomes. Several of the outcomes were based only on single studies and some important outcomes were not included (such as obesity, communicable disease, myopia and substance abuse). However, many of the studies were large and diverse in terms of geographic area and type of health outcomes assessed. Also, the direction of effects was consistently towards benefit, with minor exceptions, including a subset of males for suicide ideation (this was not statistically significant). All of these points contributed to a "Moderate" certainty of evidence judgement in both GDG subgroups.

# What is the balance between benefits and harms?
Favours SHS Favours SHS Rationale: the body of evidence collated in the systematic reviews indicated that provision of services can impact beneficially on key indicators of child and adolescent health. Again, the reviews considered a wide range of critical and important outcomes that could have gone in either direction of benefit or harm and there was no evidence of harm, although it was also possible that the lack of evidence of harm reflected a lack of measuring and/or a lack of reporting of additional possible harms. GDG members judged that the evidence favoured SHS, but both subgroups independently noted that if SHS are not implemented with fidelity to recommended standards and/or are provided by an inappropriate person, harms may result (such as a teacher responsible for SHS who does not make a life-saving referral, or a health worker who does not respect a student's rights).

# Do students value a comprehensive SHS? Possibly important uncertainty or variability Important variability
Rationale: controlled studies from HIC found evidence of a benefit of SHS on the critical acceptability outcome of user satisfaction: confidentiality (one study; 2 076 participants; OR 2.45 (CI 95%: 2.04, 2.95)); and access (students having a regular health-care provider (two studies; total 4 070; OR 1.33 (CI 95%: 1.15, 1.54)). The 10 cross-sectional studies from LMIC showed that access to SHS was variable (four studies; total 5 772), ranging from almost all students (97%) to only 5.4% of adolescents. One cross-sectional LMIC study (625 participants) found that a high proportion of students were disappointed in terms of confidentiality (62%), respect for privacy (57%), listening (85%), understanding (83%), dialogue (82%), support (79%), information (51%), empathy (43%), respect (53%) and exam time (71%). Both GDG subgroups discussed that evidence was limited, particularly in LMIC, which led Subgroup 1 to select "Possibly important uncertainty or variability". Subgroup 2 instead felt the very positive results in HIC provided some certainty that the majority of students value comprehensive SHS. However, this subgroup felt that important variability in service delivery remains, which in turn influences how students may value SHS in practice, leading to their judgement of "Important variability".

# How large are the resource requirements (costs)?
Varies Varies (such as start-up and maintenance costs) Rationale: this question was not examined in the reviews and indeed no evidence was found about it in the reviews. In their discussion, GDG members raised several points based on their experience and expertise. They noted that resource requirements may be kept relatively low if specialist health professionals are involved in staff capacitybuilding, monitoring and supervision rather than service delivery. For example, in LMIC resource requirements may be moderate or even low if a task-sharing system is created, while in HIC costs may be relatively low if SHS create access to existing health services rather than establish entirely new ones. These different factors led to a judgement of "Varies" by both subgroups. Subgroup 2 further chose to emphasize that there are likely to be large start-up costs in most settings as well as maintenance costs, but that these should be assessed in terms of benefit-cost ratios. Rationale: limited evidence on costs was found in the reviews, so both subgroups judged the certainty of the evidence for the costs to be "Very low".

# Is a comprehensive SHS cost-effective?
Favours SHS Favours SHS Rationale: four studies (total 7 704) provided moderate strength of evidence that comprehensive SHS were cost-saving. Three studies (total 483 649 participants) showed cost-benefits. Outcomes assessed included: reduced number of hospitalizations, reduced absenteeism, Medicaid savings and parent productivity. Although these studies were all based in HIC, both subgroups felt the evidence favoured SHS.

# What would the impact be on health equity? Increased Increased
Rationale: the reviews found that school-based health centres in the United States of America helped African-American children and adolescents from low-income families receive health care they may not have otherwise received, closing the gap in potential health-care disparities (67). Based on their joint experience and expertise, both subgroups further agreed that SHS are likely to increase health equity. The GDG noted that one of the roles of SHS should specifically be to work with the most vulnerable children and adolescents.

# Is a SHS acceptable to all stakeholders?
Probably yes Probably yes Rationale: in the HIC studies there were strong beneficial findings related to SHS acceptability in terms of, for instance, student use, access and confidentiality. Three cross-sectional studies from LMIC provided variable results in terms of provider or other professional satisfaction (total 928 participants). In a study in Iraq, school principals' overall satisfaction was rated as "satisfied to some extent" (82). In a second study, in Turkey, a very high proportion of teachers (337/360, 93.6%) in private schools and 338/360 (93.9%) in public schools believed that school nurses were needed (83). In a third study, in the Islamic Republic of Iran, authors reported that standards were met in 94% of schools for first-aid and screening functions of nurses, 69% for consultations with colleagues, peers and mental health consultants, 72% for health education, 76% for diagnosis and 62% for managing health planning with educational plans, but only 39% for using a suitable evaluation system for the plan for students, parents and staff (84). The GDG discussed how SHS, if designed and implemented to a high standard, might well be acceptable to most stakeholders, but there was uncertainty as to whether SHS would be acceptable to all stakeholders (such as students, parents, school staff, community members and policy-makers) as worded in the question. This influenced both subgroups' judgement of "Probably yes".

# Is a SHS feasible to implement? Varies Yes
Rationale: the systematic reviews generally found comprehensive SHS to be feasible to implement in HIC. However, they may face challenges in implementation, including time and budget constraints, children moving within and between schools, SHS staff turnover and communication challenges between SHS and school staff (about, for instance, SHS staff roles). Subgroup 2 felt that SHS nonetheless are feasible to implement and judged the answer to be "Yes". Subgroup 1 noted that similar challenges were likely to take place in LMIC, where the feasibility of SHS may be especially likely to vary between schools and between countries, depending on resources; this led to their judgement of "Varies".

# Menu and compendium of interventions

# Rationale for the menu and compendium of interventions
The reviews of national SHS described in section 1.3 showed that the health areas covered and the types of SHS activities included in national SHS programmes vary considerably between countries.
The systematic reviews of the effectiveness and acceptability of comprehensive SHS conducted to provide background information for this guideline had similar findings, as a range of SHS health areas and types of activity were described in the studies of comprehensive SHS (see Chapter 4). However, the systematic reviews identified very few studies that compared the effectiveness of SHS with different ranges of interventions. The GDG therefore found it very difficult to make specific recommendations about the preferred scope of SHS based on the literature review and systematic reviews.
In an effort to further clarify and prioritize health areas and activities that should be included within SHS, the GDG requested that WHO compile all WHO health service recommendations for 5-19-year-olds (section 3.5.1) and also conduct a global survey of SHS experts (section 3.5.2). Based on these findings, the GDG identified 94 interventions as essential in SHS everywhere (n = 71), suitable in SHS everywhere (n = 9), essential or suitable in SHS in certain geographical contexts only (n = 7) or UNSUITABLE IN SHS EVERYWHERE (n = 7) (section 3.5.3).
To assist countries and programmes as they choose which specific interventions to include in their SHS, the GDG created a menu of these interventions.
Table 6 shows the menu of interventions that the GDG identified as essential or suitable for inclusion within SHS organized by health area, type of health activity and specific GDG categorization. Web Annex H provides an expanded version of this menu with the WHO sources of interventions (section 3.5.4). Both Table 6 and Web Annex H provide a simplified overview. This at-a-glance menu is linked to a compendium in Web Annex A that details the published global WHO evidence base and specific procedures or activities for each of the 87 interventions.      Note: each of the 87 interventions is categorized in the menu by health area, type of health activity, and final GDG ranking as essential or suitable within SHS, by location. Importantly, many interventions could be placed in multiple menu cells, but for clarity, one cell is selected for each intervention. Also, for the sake of brevity, summary names of interventions have been used in this matrix; full, precise names are given in Table 7. Web Annex H (Menu of interventions with WHO sources) and Web Annex A (Compendium of interventions with WHO evidence) provide more detailed information about each intervention. HEADSSS: home, education, employment, eating, activity, drugs, sexuality, safety, suicidal thinking and depression status (assessment).

# Full wording of the interventions
The 87 interventions that the GDG identified as essential or suitable within SHS are numbered and abbreviated in the menu in Table 6 and Web Annex H, so it can be read at a glance. The full, precise wording of each intervention is given in Table 7 and Web Annex A. For example, I-69 in short form is "Referral to rehabilitation and support for disability" (Table 6), but in long form it is "Referral and support for rehabilitation, habilitation, assistive technology, assistance and support services for injured or disabled individuals (e.g. those who are visually or hearing impaired or have eye/ear problems, who have physical disabilities or motor disorders or who have injuries)" (Table 7).
In addition, for each of the 87 interventions listed in Table 7, supporting WHO publications are cited. These publications can be accessed directly for more information, but Web Annex A also compiles excerpts from the cited publications which support and elaborate on each intervention.

# Interventions organized by GDG categorization (a-c) and type of health service activity (1-7) WHO source

# HEALTH EDUCATION (CONTD)
I-15. Provision of sexual and reproductive health education (4,19,94,102,(110)(111)(112)(113)(114)(115)(116) Full GRC support I-16. Support for a health-promoting curriculum (e.g. curriculum-based sexuality education; curriculum on nutrition and physical activity) (4,39,94,97,(100)(101)(102)110,111,113,115,117) Full GRC support I-48. Provision of health education to prevent common unintentional injuries (e.g. how to prevent unintentional injuries in the home, while playing or engaged in sports and on roads) (105,108,118,119) Partial GRC support I-49. Provision of health education to prevent violence, including intimate-partner violence, sexual violence, gender-based violence, bullying and gang violence (e.g. universal information provided on prevention of violence and abuse) (98,(106)(107)(108)113,120) Partial GRC support

# SCREENING LEADING TO CARE AND/OR REFERRAL AND SUPPORT AS APPROPRIATE
I-27. Assess and ensure compliance with school entry health requirements (e.g. medical history, comprehensive physical examination and immunization) (7,100,104,121) Other WHO support I-28. Routine preventive health check-ups (e.g. at beginning of pre-school, primary and secondary school to assess physical growth, motor development, social and emotional maturation and feeding and sleep problems and to offer appropriate care or referrals), meeting WHO criteria for a screening programme (7,38,94,96,108,122) Other WHO support   (4,7,98,104,105,118,(148)(149)(150)(151)(152)(153)(154)(155)(156) Full GRC support I-57. Administration of over-the-counter and prescribed medications by a school health-care provider (7,94,96,98,127,149,155,(157)(158)(159)(160)(161) Partial GRC support I-58. Referral and support for pain control and management, e.g. headache (7,94,98,107,108,153,158) Full GRC support I-59. Referral and support for management of non-specific symptoms (e.g. diarrhoea, fever) (4,7,41,94,104,154,155,162) Partial GRC support I-61. Referral and support for management of common infections (e.g. ear, eye oral/dental, skin, throat, urinary tract) (4,7,94,107,108,123,133,155) Partial GRC support I-62. Referral and support for management of less common infectious diseases (e.g. bone infections, cholera, dengue, dysentery, helminths, joint infections, malaria, meningitis, other neglected tropical diseases, pertussis, pneumonia, rheumatic fever, septicaemia, typhoid fever, tuberculosis, viral encephalitis) (7,32,94,98,102,154,155,(163)(164)(165)(166)(167)(168)(169)(170) Partial GRC support I-64. Referral and support for chronic care of HIV-infected children (4,94,98,103,112,116,143,147,155,162,(171)(172)(173)(174)(175)(176) Full GRC support I-65. Referral and support for management of anaemia (e.g. iron supplementation) (7,41,94,100,105,107,108,(177)(178)(179) Partial GRC support  (4,7,39,94,95,98,102,104,(106)(107)(108)113,117,120,136,143,144,181,184) Full GRC support I-74. Referral and support for management of pregnancy, including the option for pregnant or parenting adolescents to continue or return to school (4,39,102,107,108,115,116,(185)(186)(187) Full GRC support I-75. Referral and support for management of sexually transmitted infection (4,104,107,108,112,120,143,144,185,(188)(189)(190)(191)(192) Full GRC support I-76. Provide short-term counselling or crisis intervention focused on mental health or situational concerns (e.g. grief, difficult transitions) (4,19,32,104,108,193,194) Partial GRC support I-78. Referral and support for management of common behavioural disorders in children (e.g. attention-deficit hyperactivity disorder) (4,19,94,98,104,159,195,196) Full GRC support I-79. Referral and support for management of emotional, anxiety and depressive disorders (4,19,32,98,102,104,144,160,181,(197)(198)(199) Full GRC support I-80. Referral and support for management of eating disorders (e.g. anorexia, bulimia) (19,94,103,107,108) Other WHO support I-81. Referral and support for management of stress (19,32,104,108,144,181,193,194) Partial GRC support I-82. Referral and support for management of self-harm and/or suicide risk (4,184,200) Full GRC support  (19,32,104,201) Full GRC support I-84. Referral and support for management of psychotic disorders (19,32,104,160) Full GRC support I-85. Referral and support for management of harmful use of a substance (e.g. alcohol, illicit drugs) (4,102,104,135,136,148,160) Full GRC support I-86. Referral and support for management of dependence on a substance (e.g. alcohol, illicit drugs) (4,102,(135)(136)(137)(138)(139)160) Full GRC support I-87. Referral and support for management of substance withdrawal (4,102,(135)(136)(137)(138)(139)160) Full GRC support

# SCREENING LEADING TO CARE AND/OR REFERRAL AND SUPPORT AS APPROPRIATE (CONTD)

# HEALTH SERVICES MANAGEMENT
I-25. Appropriate use of data at population level for planning school health (4,94,108,113,121,202) Other WHO support I-26. Collection, analysis and use of data on school health service utilization and quality of care, to monitor performance and support quality improvement and for evaluation and planning (4,7,94,96,202) Other WHO support I-60. Implementation of and support for a health-facility risk management plan linked with primary, secondary and tertiary care systems (e.g. protocol if school health services should provide essential services during complex emergencies) (4,7,94,99,101,104,105,151,154,188,(203)(204)(205) Other WHO support  (4,32,39,94,95,102,104,105,(112)(113)(114)(115)118,119,143,213,214) Partial GRC support I-20. Support for school policies that address bullying and harassment (4,7,19,94,102,105,106,(114)(115)(116)140,184) Partial GRC support I-21. Support for school policies on prevention and response to anaphylaxis (4,104,156,215) Partial GRC support  (4,7,19,39,94,97,98,101,102,104,105,107,108,143,147,160,180,193,196,197,218) Partial GRC support I-46. Counselling on nutrition, physical activity and a management plan, if needed (7,94,101,104,105,107,108) Partial GRC support

# SUPPORT FOR OTHER PILLARS OF A HEALTH-PROMOTING SCHOOL
Training school staff on first aid, hygiene promotion, etc. (4,38,105,110,113,128,151) Other WHO support I-24. Inspection of the physical environment of the school (e.g. prevention of injuries; water, sanitation and hygiene facilities) (4,7,94,98,99,106,113,119,154) Other WHO support I-77. Referral and support for child carers (e.g. students who provide unpaid support to a parent who could not manage without this help) No WHO source identified  (94,100,102,104,127,(177)(178)(179) Full GRC support

# CLINICAL ASSESSMENT LEADING TO CARE AND/OR REFERRAL AND SUPPORT AS APPROPRIATE
I-53. Referral and support for voluntary medical male circumcision (4,103,104,112,116) Full GRC support
Note: this list contains the precise wording of each intervention; the wording used in the menu is abbreviated in some instances.

# Final intervention categorization and WHO sources of the interventions

# Implementation of the WHO guideline on SHS

# Dissemination of the WHO guideline on SHS
The current guideline is being disseminated as a printed publication and also is posted with its Web Annexes on the WHO website. It will be disseminated though a broad network of international partners, including WHO country and regional offices, ministries of education and health, WHO collaborating centres, universities and other United Nations agencies and nongovernmental organizations (NGOs). The guideline has been developed in English and will be translated into other WHO official languages for wider dissemination, in collaboration with WHO regional offices.

# National adaptation of the WHO guideline on SHS
This is a global guideline, so WHO Member States are expected to adapt the SHS recommendation and intervention menu depending on their context and local feasibility. WHO regional and country offices will be able to assist with these processes.

# SHS within broader national health strategies
SHS programmes already exist in some form in most countries, so in most cases governments will not be creating a national SHS programme from scratch, but rather evaluating and strategically improving on an existing programme to become more comprehensive and evidence-based. In either case, development or improvement of national SHS programming needs to take place within the broader national strategizing for health.
WHO has produced practical guidance on national strategizing for health that can be adapted in such efforts (224)(225)(226). For example, the 2016 WHO Strategizing national health in the 21st century: a handbook publication (225) outlines key steps in national health strategizing that can be adapted to national SHS strategizing, including:
- population consultation on needs and expectations;
- intersectoral situation analysis;
- priority-setting for national policies, strategies and plans;
- strategic planning (transforming priorities into plans);
- operational planning (transforming plans into action);
- estimating the cost implications of a policy, strategy or plan;
- budgeting for health;
- monitoring, evaluation and review of policies, strategies and plans;
- law, regulation and strategizing;
- strategizing for health at subnational level;
- intersectoral planning for health and equity; and
- strategizing in distressed contexts.

# An organizational model of SHS
Fig. 5 provides a basic organizational model of SHS that shows the key stakeholders involved in SHS programming. From national to local levels, it is important that SHS are led through close collaboration of the health and education sectors. Collaboration between the health and education sectors is ideal for implementing all pillars of HPS, but to effectively provide comprehensive SHS, genuine, close collaboration of the health and education sectors is critical.

# National policy, planning and financing
In addition to the health and education sectors, other sectors also can play a valuable role in policy, planning and financing at national level, including other government ministries (such as social services, and water and sanitation), the private sector and NGOs.

# Local implementation
SHS can be implemented through different structures at local level. Most commonly, they are school-based health services -that is, services provided by on-site health personnel only, by both on-site and visiting health personnel or by visiting health personnel only (8). However, SHS may also (or instead) be provided through school-linked services; these are SHS that are not physically located within the school but are provided outside of school premises (at primary care facilities or community centres, for instance). These schoollinked SHS facilities and/or providers have a formal agreement with the school administration to provide health services to their students/learners. Trained health workers (like nurses, clinical officers, doctors, medical assistants, physical therapists, dentists, psychologists and counsellors) are expected to be the main SHS staff. They should work closely with education sector staff (including school principals, administrators and teachers) and staff from other parts of the health and social services (such as primary health care, specialist services or social workers). In addition, they need to communicate directly with parents to coordinate a student's care related to, for example, referral and follow-up.
The primary beneficiaries of SHS are students/ learners. In addition, students and their families can help to inform and monitor SHS through participatory research and other activities.

# School health services

# Prioritizing health conditions and interventions within SHS
National governments need to identify and address their particular SHS programming priorities, because:
- the nature, scale and impact of child and adolescent health needs are unique in each country;
- all governments face resource constraints, so they must make difficult choices to ensure their SHS resources are used most effectively; and
- the structure and functioning of the health system as a whole varies between countries.
There are several global documents that provide guidance on how national governments can prioritize health conditions and interventions for their population. These can be adapted by policy-makers and programme developers who are deciding which interventions should be included within SHS. Box 7 lists some key resources that can be used in this process.
For example, the global AA-HA! Guidance (4) and its annexes and appendices (19) outline how governments can prioritize adolescent health interventions through three steps: a needs assessment, a landscape analysis, and a prioritization exercise. Similarly, SHS policy-makers and programme developers can evaluate their country's particular child and adolescent health needs and context before developing -or improving upon -SHS programming. This would include:
- a needs assessment to identify which conditions have the greatest impact on child and adolescent health and development, both as a whole (by age, sex and part of the country) and among those most vulnerable;
- a landscape analysis of:
-existing school health programmes, policies, legislation, capacity and resources and how these relate to the rest of the health and education systems within the country;
-current global and local guidance on evidencebased interventions: a starting point for this process can be the menu of interventions (Table 6 and Web Annex H) and its supporting compendium (see Web Annex A), which compiles excerpts from WHO guidance specific to each intervention and cites WHO sources that can be accessed for further information; and
- priority-setting that considers:
-the severity, frequency, scale and consequences of particular burdens;
-the needs of the most vulnerable adolescents; Fig. 6 provides an overview of national SHS intervention priority setting.

# BOX 7. Resources for prioritizing interventions within national SHS programming
In addition to the menu (Table 6 6). The potential for SHS to increase health equity is described more in Box 8.
Confidentiality is another key area of SHS programming that warrants special consideration, as in any health services for children and adolescents. It is important that national SHS programmes establish procedures to ensure:
- information about students is not disclosed to third parties;
- personal information, including student records, are held securely;
- there are clear requirements for the organization of the physical space of SHS facilities, and actions to ensure visual and auditory privacy during registration and consultations with a SHS provider; and
- consultations with adolescent students accompanied by parents or guardians routinely include time alone with the adolescent (4).

# Using the menu of interventions and its supporting compendium
Box 9 provides a simplified, hypothetical example of how the menu (Table 6  2. health-care providers should consider exposure to child maltreatment when assessing children with conditions that may be caused or complicated by maltreatment, in order to improve diagnosis/identification and subsequent care, without putting the child at increased risk; and
- written information on child maltreatment should be available in health-care settings in the form of posters and pamphlets or leaflets (with appropriate warnings about taking them home in case that could compromise safety).  - Prevention and control of noncommunicable diseases: guidelines for primary health care in low resource settings, 2012 (149)
- Guideline for the management of conditions specifically related to stress, 2013 (193)
- Guideline: updates on the management of severe acute malnutrition in infants and children, 2013 (173)
- Guidelines for the treatment of malaria, third edition, 2015 (167) In the coming years, further WHO guidance is expected on national SHS strategies and programming, intervention prioritization, implementation, and monitoring and evaluation. For example, while this guideline establishes that health sector involvement and medical expertise is indispensable in SHS at all levels of a national system, the optimal leadership roles and collaboration between health, education and other sectors in national policies and local SHS programming warrants further guidance. The development of such guidance will depend in part on further research, as described below.

# SHS research
Given the large number of health areas and activities that potentially can be included in SHS, there are many topics for which further research and evidence is needed to inform SHS. Based on research gaps that were identified during development of this guideline, the GDG produced the following list of research needed. This list of research topics is not exhaustive, but instead provides important examples.

# Governance and organization
Evaluation is required of:
- outcomes associated with different forms of SHS governance (such as education versus healthsector lead, at national and local levels);
- different infrastructure or organizational models that result from differences in governance;
- outcomes associated with different SHS healthworker qualifications (like nurse and medical assistant) and different compositions of SHS teams (including qualifications, specialties and sectors);
- SHS management, including transparency, accountability and monitoring data at school and national levels, such as whether inclusion of simple, pragmatic monitoring indicators improves outcomes; and
- how effectively to meet the health needs of disadvantaged children and adolescentsincluding those who are out of school -with quality, coverage and equity.

# Standards of care, delivery modes and effectiveness outcomes
Research is required on:
- standards of care and effectiveness outcomes;
- service delivery modes and effectiveness outcomes;
- sex and age differentiation of effectiveness outcomes, including for student age groups of 5-9, 10-14 and 15-19 years, by sex;
- possible harms of SHS (related, for example, to confidentiality);
- overall impact on well-being (beyond measurement of 1-2 outcomes);
- the combined effects of an SHS package on multiple outcomes, including educational outcomes;
- the combined effects of the six pillars of HPS on multiple outcomes; and
- quality and ethical issues in SHS, such as inclusion and confidentiality.
While randomized controlled trials may be the gold standard for some forms of medical research, they may not be feasible for evaluating social or public health interventions such as SHS due to their great cost, time and complex challenges, including randomizing schools or cities to comprehensive SHS. Instead, the GDG suggests adoption of an implementation-science approach using other methods, such as controlled before-after studies and interrupted time-series studies.

# Acceptability outcomes
The following are required:
- qualitative research on student and family satisfaction or SHS acceptability;
- participatory research engaging young people on SHS priorities, best practices, acceptability and equity; and
- sex and age differentiation of acceptability outcomes for, for example, student age groups of 5-9, 10-14 and 15-19 years, by sex.