Secondary schools are sites of academic instruction but also contexts of socioemotional development, and the intertwining of these two functions has consequences for adolescents' future health and education. Drawing on nationally representative data from the National Longitudinal Study of Adolescent Health (n = 8,271), this study explored the bidirectional associations among indicators of adolescents' alcohol use and their feelings of social integration at school. Socioemotional problems did not predict increased drinking over time, but drinking predicted declining socioemotional functioning, with negative implications for adolescents' academic grades by the end of high school. These associations, however, were conditioned by aspects of school context, with drinkers feeling more marginalized in schools characterized by dense networks with low rates of drinking. (Contains 3 tables and 3 figures.)