Researchers have become increasingly interested in programs' main and interaction effects of two variables (A and B, e.g., two treatment variables or one treatment variable and one moderator) on outcomes. A challenge for estimating main and interaction effects is to eliminate selection bias across A-by-B groups. I introduce Rubin's causal model to…

Background/Context: Researchers, policymakers, and practitioners undoubtedly concur that missing school deteriorates student outcomes. And yet, in evaluating the deleterious effects of missing in-school time, empirical research has almost exclusively focused on absences, and the scant amount of empirical literature on tardiness has focused on…

Recent federal, state, and district policies that have mainstreamed English language learner (ELL) students into general, English-only elementary school classrooms have raised questions among educational stakeholders about the widespread effects of these policies. Most research has focused on the outcomes of ELL students; almost nothing is known…