Abstract
This research evaluates Mexico’s 2002 universal preschool mandate using a local difference-in-differences design to isolate policy impacts from school-entry-age effects. Although the mandate significantly boosted cognitive test scores, particularly for higher-income households not participating in Prospera (the conditional cash transfer program for the poor), it proved most effective at improving grade progression for disadvantaged groups. Specifically, boys from Prospera households saw the largest reduction in grade failure. Additionally, the reform enhanced noncognitive skills for boys from non-Prospera households, with no comparable gains for girls. Overall, the findings reveal critical gender and socioeconomic heterogeneity in early childhood educational intervention impacts.