“…Because differences between students within schools are nearly always considerably larger than are differences between schools, the school effects reported in SER studies hardly ever exceed 15% for studies based on achievement scores. For non-cognitive outcomes, the school effects are even smaller (Thomas, Smees, MacBeath, Robertson, & Boyd, 2000;Van der Wal & Rijken, 2002). This does not mean, however, that education makes only a minor contribution to the development of students.…”