How does school quality affect health amid multiple behavioral responses? The Rosenwald schools transformed school quality for rural southern African Americans in the early 1900s. Research shows that the schools made black migration northward more likely and that the Great Migration shortened life expectancy for these migrants. Besides the hypothesized health-enhancing effects of school quality, negative health effects might also occur through migration. We disentangle behavioral mechanisms and find complete exposure to the Rosenwald schools increased life expectancy by 2–3 months; a more naive approach finds no relationship. Results are robust to heterogeneous treatment effects and various measurement issues.