The purpose of this study was to explore whether school-based decision making (SBDM) impacts student achievement. Specifically, the study involved determining if the degree of teacher involvement in SBDM across eight decision dimensions differed between schools that demonstrated the most and schools that demonstrated the least district improvement in student achievement. The population consisted of elementary schools in a large urban school district with more than ten years of SBDM implementation. Student achievement scores from 1993 to 1995 were examined for all 68 elementary schools. Based on degree of improvement for fourth grade scores over the three years, 15 schools from the 25% most improved and 15 schools from the 25% least improved were selected for study. Schools from the two extreme-groups sample were matched on five demographic variables. The Teacher Involvement Participation Scale—TIPS-2 (Russell,1992), an instrument for measuring the degree of SBDM in eight different decision dimensions, was given to all certified personnel at each school. A return of 575 surveys represented 63% of the sample schools' staff. Two short questionnaires were administered to principals and SBDM teams to collect descriptive data. Findings, using MANOVA followed by univariate tests, indicated significant differences between groups in six of the eight SBDM decision dimensions. The most improved schools had a higher degree of participation (p < .01) in SBDM decisions in dimensions of: 1) goals/vision/mission, 2) curriculum/instruction, 3)standards, and 4) facilitating procedures/structures. Although neither group participated widely in decisions about staffing and operations, the most improved schools were more involved in those decisions than the least improved schools (p < .05). No significant difference was found between the two groups in the dimensions of budget and staff development. It is concluded that student achievement is positively impacted by greater participation in SBDM in at least six of eight SBDM dimensions, with "goals/vision/mission" and "curriculum/instruction" being the most critical factors. Although these findings indicate that SBDM contributes to improved student achievement, further research is needed to determine if this study's findings are supported.