Detailed participant observation among Detroit area adolescents provides explanations for the mechanisms of the spread of sound change outward from urban areas and upward through the socioeconomic hierarchy. The use of local phonological variables in adolescence is determined by a social structure within the age cohort, dominated by two opposed, and frequently polarized, school-based social categories. These categories, called “Jocks” and “Burnouts” in the school under study, embody middle-class and working-class cultures respectively, and articulate adolescent social structure with adult socioeconomic class. Differences between Jock and Burnout cultures entail differences in social network structure and in orientation to the urban area, and hence to urban sound changes. Parents' socioeconomic class is related to, but does not determine, category affiliation, and while category affiliation is a significant predictor in phonological variation, parents' socioeconomic class is not. (Variation, sound change, adolescents, urban dialects, suburban dialects, schools)