The period of compulsory education – primary, lower secondary and even the upper secondary cycle in some countries – is at the core of all education systems. Over recent years, there have been significant investments in this core phase of education, recognised as being fundamental for laying the foundation on which so many other social, economic and educational outcomes may follow. Teachers (and the educational workforce in general) are widely recognised as central to the success of schooling, a position reinforced by the major 2005 OECD study Teachers Matter: Attracting, Developing and Retaining Effective Teachers. OECD work has analysed with growing precision the characteristics of learners and the nature of school practices, including leadership. Policy orientations have stressed the need simultaneously to modernise, professionalise and innovate, while also placing reforms directed at effective learning – rather than changing only structures and administrative systems – at the core of schooling.