This study investigated the extent to which a State Systemic Initiative (SSI), a National Science Foundation program designed to improve science education across an entire state, implemented in the United States, could reform science education. Impacts that were measured included teachers' instructional practices, professional community, influence of the SSI on school policy, external influences on science instruction, and family involvement. In addition, students' views of instructional practice, school community and family involvement were measured. A retrospective comparative design was used to collect survey data from 46 middle schools: 23 that had significant amounts of contact with the SSI and 23 matched schools that had little to no contact with the SSI. The results suggested there were important differences favoring schools whose science teachers had participated in the SSI. Included were differences in the use of standards-based instruction, and external influences on science instruction teachers' influence on policy. No differences between the two groups were found for professional community or family involvement. For students, significant differences were only found for access to standards-based instruction. Results imply that SSIs can help change specific aspects of the system, but broader impacts are more difficult to achieve. © 2004 National Science Council, Taiwan.