This article systematically reviews research on the achievement outcomes of three types of classroom approaches to improving the reading achievement of students in grades 2-5: Reading curricula, computer-assisted instruction (CAI), and instructional process programs. Study inclusion criteria included use of randomized or matched control groups, study duration of at least 12 weeks, and use of valid achievement measures that were independent of the experimental treatments. A total of 80 studies met these criteria. The review concludes that programs designed to change daily teaching practices have greater research support than those that focus on curriculum or technology alone. In particular, positive achievement effects were found for cooperative learning programs and for same-age and cross-age tutoring programs. The effective approaches provided extensive professional development intended to significantly affect teaching practices. In contrast, studies of reading textbooks and of computer-assisted instruction found small effects on reading outcomes. (Contains 4 tables.)