The design of open spaces on school grounds and within school buildings should not be regarded as a marginal issue in the development of all-day schools. Rather, open spaces in schools play an extremely important role in the developmental processes of young people and thus make a significant contribution to the qualitative (further) development of all-day schools. The author theoretically encourages educators, architects, and staff of school-related administrative units to perceive school open spaces more consciously and in their comprehensive significance. Furthermore, he provides concrete recommendations for the appropriate design of school open spaces.