The purpose of this study was to conduct a longitudinal examination of the relationship between sustained after-school participation and a district's Early Warning Index associated with school dropout in a large urban school district. The study included 64,351 students participating between 2000-2001 and the 2011-2012 school years. Data were subjected to hierarchical linear modeling to determine individual student academic growth trajectories over time and the relationship to after-school participation. Results indicate that sustained yearly participation and higher days per year participation increase the likelihood that students stay on a positive academic trajectory.