Longitudinal data from a nationally representative sample of 10th graders (National Educational Longitudinal Study of 1988 First Follow-Up) were used to assess the net effect of athletic participation on student outcomes after controlling for student background and 8th-grade measures of the dependent variables. The analyses show positive effects of sport participation on grades, self-concept, locus of control, and educational aspirations, and a negative effect on discipline problems. Analysis also shows that athletic participation is unequally distributed across gender and socioeconomic groups: Males, students from higher socioeconomic levels, students attending private and smaller schools, and those with previous experience in school and private sport teams are more engaged in high school competitive sport.