We compare the adult outcomes of cohorts who were differentially exposed to policy-induced changes in Head Start and K–12 spending, depending on place and year of birth. IV and sibling-difference estimates indicate that, for poor children, these policies both increased educational attainment and earnings, and reduced poverty and incarceration. The benefits of Head Start were larger when followed by access to better-funded schools, and increases in K–12 spending were more efficacious when preceded by Head Start exposure. The findings suggest dynamic complementarities, implying that early educational investments that are sustained may break the cycle of poverty. (JEL H52, H75, I21, I26, I28, I32, I38)