By the time they reach kindergarten, disadvantaged children already show an achievement gap relative to their higher-income peers. In an attempt to level the playing field for low-income youth, some have called on policymakers to invest in early childhood education by expanding high-quality preschool access to a greater number of American families. Indeed, research has shown that expanding access to high-quality preschool programs can be a cost-effective way to narrow the achievement gap and help low-income children build skills. However, the impact of the program depends critically on a child's education in the absence of the intervention. Children with ample developmental and educational support--such as those enrolled in private preschool programs--will benefit far less from expanded access to preschool relative to those without access to high-quality preschool. In this policy memo we provide guidelines for policymakers seeking to maximize the impact of investment in early childhood education. Our framework calls for the establishment of a high-quality program in areas where programs do not exist, improved preschool quality in those states and localities with subpar programs, and expanded access in areas where high-quality programs already exist. The available evidence suggests that expansion of early education programs along these lines will lead to improved educational outcomes for disadvantaged children, in addition to a host of other social benefits such as lower crime, reduced teenage pregnancy, and a lessened reliance on the social safety net. (author abstract)