This document describes the methodology used to carry out the Assessment of School-Based Management Study, which identified the conditions in schools that promote high performance through school-based management (SBM). The 3-year project, sponsored by the U.S. Department of Education's Office of Educational Research and Improvement (OERI), began in 1991. A literature review was conducted during the first year, case-study field research was conducted during the second year, and cross-site analysis was undertaken during year three. The first phase of data collection examined how SBM, when combined with ambitious curriculum and instruction reform, could work to improve the performance of school organizations. The conceptual framework was based on Lawler's high-involvement model (1986), which focuses on increasing employee involvement in organizational decision making. The case studies sought to discover whether the high-involvement model differentiated between schools that were struggling with SBM and those that were successful with SBM. Case studies examined a total of 27 schools from 5 school districts--3 in the United States, 1 in Canada, and 1 in Australia. An average of 7 interviews were conducted per site for a total of 189 school-level interviews with the principal and assistant principal, governance council members, the union representative, a resource specialist, and teachers. A total of 47 district-level interviews were conducted with district administrators and school board members. Cross-site analysis examined data from 17 schools from 8 school districts (7 in the United States and 1 in Australia). Methods included onsite visits; observations and surveys of teachers; analysis of archival data; and a total of 303 interviews with the principal, governance council members, the union representative, department heads, teachers involved in innovative practices, and teachers not involved in innovative practices. Five tables are included. (Contains 8 references and a bibliography of 19 items.) (LMI)