We explored the extent to which intensity and breadth of participation in an after-school program (ASP) predicted academic achievement, as measured by changes in grades and attendance. The sample comprised 719 2nd-grade through 8th-grade Boys and Girls Clubs of Greater Dallas members during the 2009-2010 academic year. With respect to intensity, extent of club participation was positively related to increases in GPA from the first-week to the last 6-week grading period. This relationship was stronger for elementary students. In addition, intensity was negatively related to changes in school absences from the first week to the last 6 weeks for both grade levels. With respect to breadth, participation in greater numbers of programs was related to greater improvement in GPA, but only among elementary students, and only when program participation was substantial. Overall, the results suggest that participation in structured ASPs like Boys and Girls Clubs positively affects academic achievement. (Contains 6 tables.)