This article reports a systematic review of research on science programs in grades 6-12. Twenty-one studies met inclusion criteria including use of randomized or matched assignment to conditions, measures that assess content emphasized equally in experimental and control groups, and a duration of at least 12 weeks. Programs fell into four categories. Instructional process programs (ES = +0.24) and technology programs (ES = +0.47) had positive sample-size weighted mean effect sizes, while use of science kits (ES = +0.05) and innovative textbooks (ES = +0.10) had much lower effects. Outcomes support the use of programs with a strong focus on professional development, technology, and support for teaching, rather than materials-focused innovations. [For a related record, see ED566985.]