In this chapter, a review of research on school improvement is provided. Specifically, the principal characteristics of the main approaches to school improvement are discussed. To avoid presenting a restricted view of improvement of effectiveness, we provide a brief review of the relevant literature, which is concerned with other theoretical orientations within education that examine the process of change. We also argue that the linkage between Educational Effectiveness Research and school improvement is problematic, and thus we propose the establishment of strategies for school improvement which place emphasis on the evidence arising from theory and research. Consequently, the value of a theory-driven and evidence-based approach to teacher and school improvement is stressed. This approach could be used for designing both whole-school interventions and teacher professional development projects. For this reason, the last part of this chapter refers to the main approaches to teacher professional development, and their strengths and limitations are identified.