Purpose: Contemporary school racial segregation is a manifestation of structural racism shown to harm Black children 's health. Yet, evidence on its long-term impacts throughout life, as well as effects among children of other racial backgrounds, is sparse. Methods: Data on Black and White children were drawn from the National Longitudinal Study of Adolescent to Adult Health. Using multilevel models, we estimated associations between districtlevel school segregation and measures of short-term and long-term health, including self-reported outcomes and biomarkers. Models were run separately for Black and White children, adjusting for individual- and district-level covariates. We further carried out subgroup analyses by school racial composition (i.e., majority White vs. majority non-White schools). Results: School segregation was associated with worsened short- and long-term risk factors of chronic disease among both Black and White students in terms of exercise and body mass index, but only in majority non-White schools. Moreover, Black students in these schools demonstrated less adolescent drinking and smoking with increased racial segregation and better self-reported health in young adulthood. Discussion: Our findings suggest that segregated majority non-White schools may be targets of systemic disinvestment and may therefore lack sufficient resources for physical education or nutrition. Improvements in some outcomes among Black children may re flect peer in fluence (i.e., Black adolescents generally drink less than White adolescents), reduced exposure to interpersonal racism from White peers, or positive health fostered by feelings of belonging in Black community. Ensuring all students go to schools with the resources they need to thrive may have positive spillovers for population health. (c) 2024 Society for Adolescent Health and Medicine. All rights are reserved, including those for text and data mining, AI training, and similar technologies.