"Double-dose" English as a strategy for improving adolescent literacy: Total effect and mediated effect through classroom peer ability change.

"Double-dose" coursework has become an increasingly popular strategy to assist low-performing students succeed in academic coursework. Chicago implemented a "double-dose" English policy in 2003. This policy not only provided additional instructional time to struggling readers, but also intensified skill-based sorting in English classes. I use policy-induced variation to infer the policy effect on students' reading achievement and the effect mediated by classroom peer ability change. Results show very weak, but positive effects of taking double-dose English for students with average skills. However, potential benefits of doubled instructional time are likely to be offset by negative effects of declines in classroom peer ability. Students with very weak skills experienced minimal change in classroom peer ability, and two-period coursework is likely to benefit these students.