The Four Planes of Education, p. 1.
Dr. Montessori believed that growth, development, and learning happen in waves. She determined that children go through four distinct periods of development, which she called the planes of development. The four planes occur from birth–6 years old, 6–12 years old, 12–18 years old, and 18–24 years old. In each plane, children and youth are drawn to different skills and activities, and Dr Montessori believed that they can make enormous progress if they have opportunities to explore and practice these skills.