California has a thriving climate for middle grade reform, with most middle grade schools in the state attempting some change. In this study, we examined the reform implementation process in 17 schools where staff members had devoted considerable effort to 1 of 4 instructional reforms: heterogeneous grouping, cooperative learning, active learning, or interdisciplinary instruction. Although different combinations of external and internal pressures prompted schools to focus on a particular reform, at all schools the principal or a small cadre of teachers took responsibility for building a reform vision and for logistical activities of implementation. All 4 reforms relied heavily on teachers\u27 willingness to change daily instructional content or strategies, and teachers asserted strong ownership of changes, rejecting prepackaged guidelines and resources. Implementation problems varied according to the specific reform area, with heterogeneous grouping and interdisciplinary instruction posing the greatest challenges to staff members
