California has fallen behind on many key indicators of education performance, prompting policymakers to look for strategies to improve student outcomes. This research brief summarizes the fourth and final report from the California Preschool Study, synthesizing findings from earlier reports, and recommending policies to improve preschool education in the state. Reported findings include: (1) Disadvantaged children, who are more likely to start school behind and stay behind, are also the least likely to attend high-quality preschool programs; (2) California's underfunded preschool system serves only half the eligible three- and four-year-olds, and the system does not reward higher-quality providers; (3) Increasing access to high-quality preschool for disadvantaged children can narrow existing achievement gaps; (4) In the short term, California can allocate existing resources more efficiently and provide infrastructure supports for raising quality in the future; and (5) In the longer term, new resources should be used to expand access to and raise the quality of preschool programs for those who can benefit most. (Contains 2 figures.) [This research brief describes work done for RAND Labor and Population and documented in "Preschool Adequacy and Efficiency in California: Issues, Policy Options, and Recommendations," Lynn A. Karoly, 2009. For the full report, see ED505481.]