Participation in Organized Activities (OA) is associated with positive behavioral and developmental outcomes in children. However, less is known about how particular aspects of participation affect the academic achievement of high school students from different social class positions. Using the Education Longitudinal Study of 2002, this study examines the math achievement gains from organized activity participation for advantaged and disadvantaged youths. Findings indicate that the relationship between OA and achievement does indeed vary by social class. Regardless of the type of OA, less advantaged high school students see substantial academic improvements from time in OA while their more advantaged peers do not. These findings suggest that participation in organized activities is a form of resource compensation that helps to reduce the achievement gap between advantaged and disadvantaged youths, even at the end of the K-12 schooling process.