The aim of this book is to contribute to the advancement of educational effectiveness theory by discussing different strategies: including alternative theoretical models to understand educational in/effectiveness, extending the methodology to analyze processes and mechanisms of educational in/effectiveness, analyzing differential effects of processes and instruments on educational in/effectiveness, carrying out complex multivariate analyses considering manifest and latent variables, and combining theory and practice in real school situations. Taken together, the strategies presented in this book make it clear that the advancement of educational effectiveness theory depends on the advancement of educational effectiveness methodology, or in other words: from theory to methodology and from empirical evidence back to theory. This book was originally published as a special issue of