The results of a case study in an elementary school indicate that parents can effectively support school improvement efforts even in schools with characteristics identified in previous research as inimical to change. Administrators, teachers, and parents were interviewed about the impact of a five-part plan developed by the school's parent teacher association. The plan called for (1) awarding grants to teachers for trying new practices, (2) holding a schoolwide student awards program, (3) supporting increased use of computers in instruction, (4) continuing a publicly recognized exploratory program suggested by the principal, and (5) sponsoring social functions at which teachers could be recognized. From the literature, researchers developed a list of change variables whose impact on the PTA-initiated change process could be assessed through interviews. These variables included school culture, power and control, the clarity of the proposed changes, teacher participation, the degree of collaborative planning involved, the presence of support activities and training, the change's impact on teacher efficacy, the school's team spirit, and instructional leadership. This report reviews the literature, cites the critical incidents in the change process, assesses the impact of each variable, and summarizes the factors responsible for the effectiveness of the PTA effort. (PGD)