In recent years, many states and districts have established or expanded state- and locally funded prekindergarten programs, with the goal of improving children's school readiness. A small body of research suggests that these programs have achieved small to moderate impacts on children's literacy, language and numeracy outcomes ( 10-13 ). We report findings from a rigorous large-scale quasi-experimental study of the impact of one such program on children's school readiness. We make several important contributions to the literature. First, using a regression-discontinuity (RD) design, with a birthday cutoff for entry into the program in a given year providing exogenous assignment to the treatment and control conditions, we present the first evidence of the causal impacts of a publicly funded prekindergarten program on essential components of school readiness besides mathematics, literacy, and language, such as executive functioning and emotional readiness. Second, we possess detailed information on the counterfactual condition. Unlike prior studies, we can describe in detail what kinds of services control group children received. Third, because the prekindergarten program was the first in which explicit curricula were implemented across study classrooms, our study provides practical guidance about the conditions under which prekindergarten programs can achieve positive causal impacts at scale. Finally, our findings are robust to critical methodological issues that have gone unexamined in prior evaluations of similar publicly funded prekindergarten programs.

We found that the prekindergarten program had substantial impacts on children's mathematics, vocabulary, and early reading skills, with effect sizes around half a standard deviation higher. The program also had small impacts on multiple dimensions of children's executive functioning and emotional development. In addition, on some outcomes, the impacts we detected were considerably larger for specific subgroups of children, including those eligible for free/reduced lunch, and for Asian and Hispanic children. In sensitivity analyses, our results were robust to a variety of critical threats to internal validity. Our results inform important curricular decisions that must be made when public prekindergarten programs are implemented. For policymakers, our results confirm that publicly funded prekindergarten programs can improve subsequent educational outcomes for children in meaningful and important ways.