To determine if the Teen Outreach Program (TOP), a youth development and service learning program, can reduce sexual risk-taking behaviors compared with a business as usual or benign counterfactual. We synthesized results of 5 independent studies conducted in 5 geographically and ethnically diverse locations between 2011 and 2015 with 17 194 middle and high school students. Each study cluster-randomized classes, teachers, or schools to treatment or control groups and included the students enrolled in those clusters at baseline in an intent-to-treat analysis. Multilevel models tested impacts on recent sexual activity, recent unprotected sexual activity, and sexual initiation among the sexually inexperienced at baseline at approximately 1 and 2 years after baseline. Precision-weighted average effect sizes showed nonsignificant reductions of 1 percentage point or less in recent sexual activity (5 studies: -0.6; P = .32), recent unprotected sex (5 studies: -0.2; P = .76), and sexual initiation (4 studies: -1.1; P = .10) after 1 year. There was little evidence of the effectiveness of TOP in reducing sexual risk-taking behaviors. Results underscored the importance of continually evaluating evidence-based programs that have previously been shown to be effective.