To become successful learners, students need to comprehend what they read. Children from disadvantaged backgrounds, in particular, may have difficulty comprehending text because they often lack general vocabulary and strategies for organizing information and gleaning knowledge from text. This report, from Mathematica’s federal study of four reading comprehension programs, sheds light on the effectiveness of these curricula in helping disadvantaged students improve their reading comprehension. Overall, the curricula had no positive impact on student test scores, and in some cases, had a negative impact. The study, a large-scale randomized control trial involving 268 teachers and 6,350 students in 89 schools in 10 mostly large disadvantaged urban districts in 8 states, examined the effects of these curricula on fifth-grade students.