Though student engagement is hypothesized to be a factor in explaining student level differences in afterschool programs, the measurement of student engagement in this context is inconsistent, and findings from the small number of studies about how engagement impacts developmental and academic outcomes are mixed. In this study, we tested the factor structure of Wang and colleagues' school engagement scale with a sample of middle school students (N = 197) who attended an afterschool program in an urban setting. Results suggest that a bifactor model of engagement best fits the data, meaning that engagement consists of four specific factors (affective, behavioral, cognitive, social) and a global factor. We then used structural equation modeling to examine the relationship between engagement, academic outcomes, and positive youth development (PYD). (author abstract)