Unlike organized activities such as sports and arts, civic activities in adolescence (e.g., volunteering, student government) have been less studied in relation to school success and almost all existing evidence consists of cross-sectional findings. In a longitudinal study, 1035 pupils (64% females, 20% nonwhite, M[subscript age] = 14.21 years) from high schools reported their engagement in organized non-civic and civic activities during the school year, dimensions of activity participation (e.g., intensity, duration, motives), and covariables (age, gender, ethnicity, SES, self-esteem, parental relationship, school motivation). Previous and end-of-year grade point average (GPA) were collected from school administrations. Results revealed that both civic and non-civic organized activities independently predicted increases in GPA over the school year, even after adjusting for all covariables.