“…The original methodological framework for SGPs is quantile regression (QR), and an R package (Betebenner, VanIwaarden, Domingue, & Shang, ) has been developed in support of the methodology. Within this framework, which has been the focus of several recent research efforts (e.g., Castellano & Ho, ; McCaffrey, Castellano, & Lockwood, ; Shang, VanIwaarden, & Betebenner, ), SGPs are calculated in multiple steps. First, student scores are generated for each year's test.…”