The Action Research on Change in Schools (ARCS) project was a collaborative action research study that involved two levels of research: a specific research project in each of two junior high schools in Michigan and New Hampshire, and a simultaneous study of the collaborative action research process itself as it relates to teachers' individual stages of development. Both teams involved all staff members in research activities that focused on evaluation studies of school-based scheduling issues and their effect on curriculum and instruction. Three empirical measures assessing moral judgment, ego development, and conceptual complexity were administered to all participating teachers, and a variety of documentation techniques were used to record and monitor the process of action research in each team. This executive summary presents findings from both levels of the study. First, a comparison is presented of teachers at each of the four stages of development: conventional, transitional, goal-oriented, and self-defining. Next, the collaborative action research process is described, along with teacher-perceived outcomes in the areas of school context, collegiality, teachers as action researchers, and collaborative action research. A discussion ensues of collaborative action research as it relates to staff development and school improvement. The report concludes with implications of the findings for principals and school administrators and for staff developers, teacher educators, and researchers. References are included. (TE)