Summer youth employment programs (SYEPs) are believed to have the potential to improve the behavioral, economic, and academic outcomes of the populations they serve, particularly for inner-city, low-income, and non-white youth. As part of an embedded randomized controlled trial, during the summer of 2015, I collected survey data for both the treatment and control groups from the Boston SYEP and linked this to administrative data on criminal justice outcomes. In terms of short-term program effects, participants in the program reported improved social skills and attitudes toward their communities, enhanced job-readiness skills, and higher academic aspirations. In terms of longer-term outcomes, those in the treatment group exhibited significant reductions in the number of arraignments for violent crimes (-35 percent) and property crimes (-57 percent) during the 17 months after program participation. In all cases, these gains were significant relative to the control group, and many of the largest gains were among African American and Hispanic males. Moreover, the reductions in subsequent criminal activity were greater for youth in the treatment group who reported positive improvements in social skills during the summer of participation, including how to manage their emotions and how to resolve conflict with a peer. These results give researchers some insights into a broader set of short-term program effects while also providing a look inside the "black box" as to how SYEPs affect youth over the course of a summer.