Development and evaluation of an integrated early childhood development and violence prevention teacher-training intervention in Jamaican preschools The 'Irie Classroom Toolbox' is a universal violence prevention programme, developed for use in low and middle-income countries (LMIC), which involves training preschool teachers in classroom behaviour management and in how to promote young children's social-emotional competence.  We recently conducted a study in Jamaica in which 76 preschools were randomly assigned to either receive training in the 'Irie Classroom Toolbox' (38 schools, 115 teachers) or to receive the training at a later date (38 schools, 114 teachers). We found that teachers trained in the 'Irie Classroom Toolbox' used 67% less violence against children (including physical punishment, verbal abuse and intimidation) than teachers who did not receive the training. Furthermore, the training led to significant improvements to the emotional and organisational climate of the classroom, and to observations of children's class-wide prosocial skills. A random sample of children was evaluated (n=865) and benefits of intervention were found for children's inhibitory control and for the proportion of children with clinical level behaviour difficulties.  Although significant benefits were also found to the instructional support offered by intervention teachers; the scores for both intervention and control teachers were low (<2 on a 7-point scale); indicating that cognitive and language stimulation was inadequate.  To maximise the effectiveness of the 'Irie Classroom Toolbox' to promote children's development across the cognitive and language domains in addition to the social and emotional domains, teachers need additional training. In this study, we plan to evaluate a module on instructional support which will include include i) how to promote children's higher order thinking and cognition, ii) how to provide feedback to expand child learning and understanding and iii) how to facilitate children's language development.   20 preschools who been trained in the 'Irie Classroom Toolbox' will be randomly assigned to a group in which teachers receive training in instructional support (10 schools, 30 classrooms) or a second group that will receive no additional training (10 schools, 30 classrooms). A random sample of 5 children per class will also be evaluated (300 children; 150 in each group). The intervention involves 2 full-day training workshops and 4 in-class support sessions (once a month for four months).  We will evaluate the effect of the intervention on teachers' use of the instructional strategies during teaching and learning activities. We will also evaluate the selected children's school readiness and language skills. To monitor that this additional training does not reduce teachers' behaviour management skills, we will measure teachers' use of violence against children and child behaviour difficulties in both groups. We will document factors relating to the implementation of the intervention on an on-going basis including teachers' engagement with the material, their strengths and needs in implementing the strategies and barriers and enablers to implementation.  Through this study we will investigate the acceptability, feasibility and effectiveness of the intervention and we will use the data to develop intervention manuals that are suitable for national dissemination including materials for teachers (e.g. activity guides) and materials for trainers (e.g. training manuals). The enhanced 'Irie Classroom Toolbox' produced through this study will be a teacher-training programme to i) prevent violence against children by teachers, ii) prevent the early development of antisocial behaviour and iii) promote children's social, emotional cognitive and language skills in early childhood classrooms. The intervention will be suitable for use with poorly trained teachers, working in poorly resourced settings in LMIC. The outputs of this study will make a strong contribution to the global agenda on violence prevention and the global goal of improved child development. The Global Challenges Research Fund (GCRF) supports cutting-edge research to address challenges faced by developing countries. The fund addresses the UN sustainable development goals. It aims to maximise the impact of research and innovation to improve lives and opportunity in the developing world.