This work describes a number of international comparative studies of pupils’ achievement, and examines the factors associated with successful teaching and learning and with school effectiveness. It describes the usefulness of such studies for policy makers, test designers, researchers and teachers, while offering a realistic and critical account of their limitations. Both large and small scale studies are considered, and particular attention is given to the contribution that international comparative research can make to raising the standards of work, especially in school science and mathematics, in different educational systems.