Begun in 1965 as a part of the effort to fight poverty, Head Start is the centerpiece of federal early childhood programs. Head Start’s primary goal is to improve the social competence of children in low-income families, that is, their everyday effectiveness in dealing with both their present environment and later responsibilities in school and life. Social competence takes into account the interrelatedness of cognitive and intellectual development, physical and mental health, nutritional needs, and other factors. To support its social competence goal, Head Start has delivered a wide range of services to over 15 million children nationwide since its inception. These services consist of education and medical, dental, nutrition, mental health, and social services. Another essential part of every program is parental involvement in parent education, program planning, and operating activities. Head Start services are provided at the local level by public and private nonprofit agencies that receive their funding directly from HHS. These include public and private school systems, community action agencies, government agencies, and Indian tribes. In fiscal year 1996, grants were awarded to about 1,400 local agencies, called grantees. Head Start grantees are typically required to obtain additional funding from nonfederal sources to cover 20 percent of the cost of their programs. The Head Start program works with various community sources to provide services. For example, some programs coordinate with public health agencies to obtain health services, while other programs contract with local physicians. Although all programs operate under a single set of performance standards, local programs have a great deal of discretion in how they meet their goals, resulting in great variability among programs. Although the program is authorized to serve children at any age before the age of compulsory school attendance, most children enter the program at age 4. The law requires Head Start to target children from poor families, and regulations require that 90 percent of the children enrolled in each program be low income. By law, certain amounts are set aside for specific subpopulations of children, including those with disabilities and Native American and migrant children. In addition to providing services to children and families, Head Start also sees one of its roles as a national laboratory for child development. Consequently, Head Start uses much of its discretionary research funding for demonstrations and studies of program innovations. Although overall funding has grown over the years, the amount of funds allocated to research, demonstration, and evaluation has represented about 2 percent or less of the Head Start budget. In fiscal year 1996, Head Start’s research, demonstration, and evaluation budget totaled $12 million (see app. II). Today’s Head Start is a much different program than it was 30 years ago. Although the program’s goals have changed little since its inception, Head Start changed considerably during its first decade. Begun as a summer program, Head Start became largely a full-year program by the early 1970s. In addition, in the early to mid-1970s, the program launched improvement initiatives, including promulgation of performance standards and teacher credentialing. Programs also had the option of providing home-based services. In the 1990s, the program continues to change. In 1990, the Congress passed the Head Start Expansion and Quality Improvement Act, which reauthorized Head Start and set aside funds for programs to use to enhance and strengthen the quality of services. In 1994, the Congress established a new program—called Early Head Start—to serve low-income families with infants and toddlers. The program provides continuous, intensive, and comprehensive child development and family support services to low-income families with children under age 3. In addition to changes to Head Start over the years, other changes affecting the program relate to the children and families Head Start serves and the amount appropriated to support the program. Head Start’s service population has become increasingly multicultural and multilingual and is confronted with difficult social problems such as domestic violence and drug abuse. Moreover, the number of children served by the program has grown dramatically—from 349,000 children in 1976 to about 750,000 in 1995. The amount appropriated for the program, which totaled $3.5 billion in 1995, has paralleled the growth in the number served (see fig. 1). In the decade after Head Start’s inception, many studies of the program’s impact were conducted. One of the first major studies was conducted for the Office of Economic Opportunity by the Westinghouse Corporation in 1969. This study found that summer Head Start programs produced no lasting gains in participants’ cognitive or affective development and that full-year programs produced only marginal gains by grades one, two, and three. Several researchers criticized this study because of its methodology. Subsequently, many other studies investigated Head Start’s impact. In 1981, HHS contracted with CSR, Inc., to synthesize the findings of Head Start impact studies. CSR concluded that Head Start participants showed significant immediate gains in cognitive test scores, socioemotional test scores, and health status. Cognitive and socioemotional test scores of former Head Start students, however, did not remain superior in the long run to those of disadvantaged children who did not attend Head Start, according to CSR. In addition, on the basis of a small subset of studies, CSR reported that Head Start participants were less likely to be retained in grade and less likely to be placed in special education. Because these research studies were conducted during Head Start’s infancy, their findings provide little information on the effectiveness of the current program. For instance, most of the programs included in the Westinghouse study were summer programs. Almost all programs today are full-year programs. Similarly, the great majority of studies in CSR’s synthesis study were late 1960’s and early 1970’s programs and therefore would not have reflected many significant program changes that took place in the early to mid-1970s. Interest in Head Start’s impact has grown with increased congressional and public concern for substantiating federal program performance. Traditionally, federal agencies have used the amount of money directed toward their programs, the level of staff deployed, or even the number of tasks completed as some of the measures of program performance. At a time when the value of many federal programs is undergoing intense public scrutiny, however, an agency that reports only these measures has not answered the defining question of whether these programs have produced real results. Because today’s environment is results oriented, the Congress, executive branch, and the public are beginning to hold agencies accountable for outcomes, that is, program results as measured by the differences programs make. The Congress’ determination to hold agencies accountable for their performance lay at the heart of two landmark reforms of the 1990s: the Chief Financial Officers Act of 1990 and GPRA. With these two laws, the Congress imposed a new and more businesslike framework for management and accountability on federal agencies. In addition, GPRA created requirements for agencies to generate the information congressional and executive branch decisionmakers need in considering measures to improve government performance and reduce costs. The body of research on current Head Start is insufficient to draw conclusions about the impact of the national program. Drawing such conclusions from a body of research would require either (1) a sufficient number of reasonably well-designed individual studies whose findings could appropriately be combined to provide information about the impact of the national program or (2) at least one large-scale evaluation using a nationally representative sample. Findings from the individual studies we identified, however, could not be appropriately combined and generalized to estimate program impact at the national level. In addition, no single study used a nationally representative sample, permitting findings to be generalized to the national program. The body of studies was inadequate to assess program impact by combining the findings of studies using similar outcome measures. The total number of studies found on Head Start impact was too small to permit generalizing findings to the national program. Most of these studies targeted cognitive outcomes, leaving other outcome areas, such as health and nutrition, scarcely examined. In addition, all the studies suffered to some extent from methodological problems that weakened our confidence in the findings of the individual studies. Although the body of literature on Head Start is extensive, the number of impact studies was insufficient to allow us to draw conclusions about the impact of the national Head Start program. Such an aggregation of findings should be based on a large number of studies. The larger the number of studies, the greater the chance that the variability in Head Start programs would be represented in the studies. Conversely, the smaller the number of studies, the greater the risk that the aggregate findings from these studies may not apply to Head Start in general. Most of the approximately 600 articles and manuscripts about Head Start that we identified could not be used to answer questions about impact for various reasons. Much of this literature consisted of program descriptions, anecdotal reports, and position papers. Of those articles that were research studies, some (for example, case studies) were not suitable for drawing general conclusions about impact. Some studies examined change in outcome measures before and after Head Start but did not control for other plausible explanations for the change, for example, maturation. Other studies using a comparison group to control for competing explanations of change did not provide statistical information about the confidence that the differences found were not chance occurrences. Only 22 of the more than 200 manuscripts we reviewed met our criteria for inclusion in our analysis. (See app. I for a detailed description of inclusion criteria.) Of these, 16 investigated impact by comparing Head Start participants with an unserved comparison group; 3 analyzed gains on normed tests. Only three studies included comparisons of Head Start with some other type of preschool or day care program. These studies represent work by a variety of researchers, including college students, college faculty, and contractors. Appendix III contains more detailed information on each study. Although Head Start provides services in several outcome areas, such as health, nutrition, education, and the like, most of the studies we found focused on educational/cognitive outcomes, and few made distinctions on the basis of differing populations served by Head Start.