This document reviews research on improving schools facing challenging circumstances. It discusses three phases of school improvement research: an initial focus on organizational change; a second phase integrating effectiveness research; and a current "third age" focusing on pupil outcomes, teacher instruction, building capacity, and cultural change. The findings section analyzes studies of improving, effective, and less successful schools. Key features of effective improvement programs include a shared vision, monitoring progress, strategic planning, and performance indicators to track changes over time. The document aims to identify universal principles of improvement while acknowledging the need to tailor approaches to specific school contexts.