The Effects of Preschool Education: What We Know, How Public Policy Is or Is Not Aligned With the Evidence Base, and What We Need to Know.

Early childhood education is at the nexus of basic developmental science, policy research and analysis, and the applied disciplines of education and prevention science. The field has become one of the most vibrant areas of scientific activity in terms of the connections among scientific advances and theory, program design, policy, and classroom practices. But despite the potential links between research and evaluation on the one hand and program development, practices, and public policy on the other, there are too many key areas in which public policy and practice are not well aligned with the knowledge base. These misalignments, as well as a host of questions emerging from new areas of scientific development (e.g., connections between physiological or genetic processes and behavioral development) and practice-based realities (e.g., the need for focused, intensive, and effective professional development of teachers), point to areas in which new research is needed. The aim of this monograph is to provide an analysis of the research evidence in four major domains of work in early childhood education, identifying points at which evidence is not well aligned with public policy or practice, and a set of questions to guide the next wave of research in this rapidly growing field. Overall features of the preschool landscape, including those tightly regulated by policy (such as entry age or eligibility) and those more directly related to child outcomes (such as quality of classroom interactions), are stunningly variable across settings and across time. Reasonable evidence suggests that these features also vary as a function of family background factors. The resulting picture is one of too many children and families falling through too many cracks and seams at too many levels. Thus, even in a policy and program development environment in which early education is valued and prominent and recognition of the need to close gaps and seal seams is growing, the realities point to a fragile and vulnerable nonsystem through which many of our most fragile and vulnerable citizens pass. Demographic shifts will place tremendous pressure on early education and child care in the United States in the coming decades—a trend that is well under way in many states. The consequences for preschool program eligibility and enrollment, available slots, preparation and support of staff, and program resources such as curricula are enormous. It is abundantly evident that the features of the preschool landscape—connections among child care, preschool, and schools; links between families and the adults who teach their children; capacities of the ‘‘system’’ for fostering positive development in children who increasingly vary by race, culture, language, and economic background—will undergo tremendous strain. The pressures imposed on this context and these relationships by the sheer variability present in the children and families will itself be a considerable threat to the viability of the capacity of preschool to promote positive developmental change. Compelling evidence from well-controlled research shows that preschool programs have lasting positive effects on young children’s cognitive and social development. The evidence comes from studies of child care, Head Start, and public school programs using a wide range of research methods, including experiments. Lasting positive impacts have been found for large-scale public programs as well as for intensive programs implemented on a small scale, but even some of the intensive small-scale interventions were public school programs. Some evidence has shown negative effects on social behavior, but the negative effects have not been confirmed by experimental studies. Cost–benefit analyses have shown that