The present study examined (a) the predictive effect of disruptive boys' attendance to a prevention program (i.e., dosage) on post-intervention academic achievement and behavior and (b) the potential moderating effects of child and family characteristics in this context. The 3-year intervention program included reading, self-regulation, and social skills training for the boys, parental support and skills training for parents, and teacher support. A multiple-screening procedure selected 58 disruptive, low socioeconomic status boys at the age of 6 years for program participation. Multiple regression analyses and logistic regression analyses showed that the number of program sessions attended did not contribute to the prediction of boys' post-intervention disruptive behavior. However, the number of attended sessions was positively related to boys' post-intervention likability, as well as to their post-intervention writing, reading, math, and human science performances. Interaction terms revealed that family constellation moderated the link between program dosage and likability and math success, respectively, whereas boys' IQ moderated the links between dosage and boys' success in writing and math. The discussion stresses the importance of dosage-effect analysis and the examination of moderating variables in this context.