The priority programme The educational quality of schools has been established seven years ago by the German Research Foundation (DFG). The projects in this programme investigated conditions inside and outside of school and their impact on the development of mathematical, scientific, and cross-curricular competencies.In this book major findings of the programme are presented. The projects not only give an overview of their research questioning methods and findings, but also of approaches and materials that have been developed to support learning and teaching in mathematics and science class rooms.The studies reported here identify factors for weaknesses in the educational outcomes that became apparent in the international comparisons like TIMSS and PISA. The projects, however, provide empirically substantiated units on approaches that can help to improve the educational quality of schools.