Facing mounting evidence that California has fallen behind on many key indicators of educational performance, policymakers and the public share considerable interest in exploring whether California should expand public funding for preschool education. This expanded funding will be most effective if resources can be directed to their most efficient uses. Doing so requires an understanding of how resources are currently allocated, what educational objectives preschool education can help achieve, and where preschool resources can be most effective. To investigate these issues, the RAND Corporation undertook a multicomponent study called the California Preschool Study to examine the adequacy and efficiency of preschool education in California. Researchers completed three studies to advance knowledge of (1) gaps in school readiness and achievement in the early grades among California children and the potential for high-quality preschool programs to close existing gaps, (2) the use of early care and education (ECE) services among California’s children and the quality of those experiences, and (3) the system of publicly funded ECE programs in California in the two years before kindergarten entry. The objective of this analysis, the fourth and final study component, is to integrate the results from the series of studies, as well as relevant prior research, and make recommendations to advance preschool adequacy and efficiency in California.