This book focuses on the process of change. In particular, how schools and the individual teachers who make them up experience and manage the change process brought about by their involvement in professional development programmes. The context for the study was the Intermediate Numeracy Project (INP); a project initiated by the Ministry of Education that was designed to enhance the teaching of numeracy and improve student achievement in mathematics in New Zealand schools. Models of change for a whole school and individual teachers were outlined in the literature review. Key catalysts and barriers to the change process were also identified. Barbara Rogoff’s (1995) method of three plane analysis relating to processes at the personal, interpersonal and community level was used as a framework for the research results. Although this study focused on the teachers in one school, the findings should provide useful insights for schools, teachers, school leaders,and professional development facilitators who grapple with reforms in teaching and learning and curriculum change, not only within numeracy and mathematics but within the broader school curriculum.