Margaret McMillan believed that children learn best through hands-on experiences and active learning. She valued the role of parents and advocated for healthy eating, balanced meals, and access to a wide range of materials for children to explore freely. McMillan opened centers providing outdoor sleeping and play areas for children to improve their health. Her nursery schools emphasized outdoor play and exploration in large gardens without formal structures, allowing children time to play, run, and experience nature. McMillan's philosophy influenced the development of nurseries with open-air classrooms, gardens, and routines for meals, sleep, and active outdoor play.