One of the main findings of the study was that although both the intensity and breadth of participation in organized activities decreased over time, the intensity of participation showed steeper declines by later grades. A second main finding was that youths with initial levels of participation (both intensity and breadth) in organized activities in early adolescence were more committed to school and developed more positive values toward society by the 11th grade than those who participated less. This might suggest that a high level of participation in organized activities during early-to-mid-adolescence is particularly important for later positive developmental outcomes. The study determined the growth curves of intensity (number of hours spent in an organized activity) and breadth (number of different types of organized activities) of participation in organized activities from grades 7 though 11. Associations were then determined between the intensity and breath of participation in organized activities over this time span and measures of academic orientation, risky behaviors, internalizing problems, and civic involvement. The study involved a homogenous sample of 299 youth (62 percent girls) with a mean age of 13.37. The survey was administered annually with questionnaires and phone interviews. The four indicators of academic orientation were grades, educational aspirations, self-perceptions of academic competence, and skipping class. Risky behaviors measured were antisocial behaviors, substance use, and unsafe sex. Internalizing problems measured were depressive symptoms, self-worth, and loneliness. Measures of civic development were commitments to civil society, environmental sustainability, and altruism. 4 tables, 1 figure, and 37 references