I use Danish administrative data to investigate the consequences of summer camp participation combined with a one-year follow-up program for disadvantaged boys on academic, personal, and social competencies. My identification strategy relies on individual-level panel data that enable me to observe outcomes before and after summer camp participation. Using a difference-in-differences strategy, I find overall positive effects on academic and personal competencies that reduce the gap to a matched group of boys with similar background characteristics by 40 to 80 percent. Further, I exploit a structural change in the follow-up program to evaluate how different mentoring strategies affect outcomes. In 2017, the follow-up program was changed from individual mentoring to group mentoring. Using a triple differences strategy, I find that group mentoring in the follow-up program improves personal and social competencies, suggesting that the format of the follow-up program is crucial for effects on personal and social competencies.