Analyzing Complex Treatment Effects in Nonrandomized Observational Studies: The Case of Retention of Students in Grade.

Should low-achieving students be promoted to the next grade or be retained (held back) in the prior grade? This special section presents a discussion of the application of marginal structural models to the challenging problem of estimating the effect of promotion versus retention in grade on math scores in elementary school. Vandecandelaere, De Fraine, Van Damme, and Vansteelandt provide a didactic presentation of the marginal structural...