This introduction presents an overview of the key concepts covered in the subsequent chapters of this book. The book considers the role of teacher collaboration and teacher leadership within education reform, improvement and change. The failure of a great deal of contemporary education reform and change largely stems from the fact that practitioners' views are not adequately considered and teachers are not leaders of the reform process. While 30 years of evidence from the school effectiveness and school improvement field has undoubtedly shaped and influenced education policy making for the better, there are still significant challenges facing those charged with raising educational attainment and achievement. In their writing, Hargreaves and Fullan propose that the group is far more powerful than the individual in school and system change. What constitutes a Professional learning community (PLC) tends to vary and wander considerably in the international literature, often to the point where, as DuFour proposes, it is in danger of losing all meaning.