This study examines whether attending preschool enhances the cognitive abilities, health and socialization of junior high school students in China. Using propensity score matching to control for a rich data set of student, family and school characteristics, I find that attending preschool enhances cognition among seventh graders but those gains fade among ninth graders. The greatest benefits from preschool accrue to both seventh and ninth graders from economically disadvantaged families. Results for non-cognitive categories are mixed, and no evidence suggests superior health outcomes. Evidence also shows cognitive benefits among adolescents -- especially those economically disadvantaged -- who entered preschool earlier. (author abstract)