Participation in high school sports had positive effects on many Grade 12 and postsecondary outcomes (e.g., school grades, coursework selection, homework, educational and occupational aspirations, self-esteem, university applications, subsequent college enrollment, and eventual educational attainment) after controlling background variables and parallel outcomes from Grades 8 and 10 in a large, nationally representative, 6-year longitudinal study. In contrast to Zero-Sum and Threshold Models, these positive effects generalized across academic and nonacademic outcomes, across the entire range of athletic participation levels, and across different subgroups of students (e.g., SES, gender, ethnicity, ability levels, educational aspirations). Sport participation is hypothesized to increase identification/commitment to school and school values which mediate the participation effects, particularly for narrowly defined academic outcomes not directly related to sport participation. Consistent with this Identification/Commitment Model, extramural sport, and to a lesser extent team sport, had more positive effects than intramural and individual sports. (PsycINFO Database Record (c) 2016 APA, all rights reserved)