This article examines the relationship between after-school program quality, program attendance, and academic outcomes for a sample of low-income after-school program participants. Regression and hierarchical linear modeling analyses use a unique longitudinal data set including 29 after-school programs that served 5,108 students in Grades 4 to 8 over 2 years. Program quality measures, based on activity observations, include supportive environment, opportunities for purposeful engagement, and structured interactions. Findings suggest that middle school students attend programs with greater purposeful engagement less often, while attendance for younger students is less sensitive to program quality. Greater purposeful engagement is associated with lower test scores for elementary and middle school students. In contrast, a more supportive environment and greater opportunities for structured interactions relate to improvements in test scores. Findings are discussed in light of ongoing policy debate regarding the proper focus of after-school programs and concerns about poor program attendance. (author abstract)