Background: Previous research has identified individual and school-level characteristics that are associated with sexual risk-taking, but the impact of school-level mechanisms on sexual risk-taking is not well understood. We examine the aggregated effects that early sex at the school level have on risky sexual behaviors. Methods: We use 3 waves of data from the National Longitudinal Study of Adolescent Health. An individual's first sexual intercourse before age 15 was recorded along with various risky sexual behaviors at debut. Two variables at respondent's later stage of life were also included: having sex in exchange for drugs or money, and contraction of sexually transmitted disease (STD). Longitudinal analysis was conducted using a joint parameter model that tested unobserved school effects on individual behaviors simultaneously. Results: An increase in early sexual initiation at the school level was associated with higher probability of sexual debut, along with increased involvement in sexual risk-taking controlling for student family background. Conclusions: School behavioral mechanisms are directly related to sexual health behaviors among youth. Our findings have implications for school-based interventions, education programs, and the role of parents.