The four planes of development are an overall vision of Montessori’s developmental psychology and provide a framework or structure for understanding her theory of human development, ages 0-3,3-6, 6-12, 12-18, 18-adulthood. (Kahn, D., 2022). Each plane has its own special characteristics and needs. The planes are: (1) Ages birth to 6 years of age, the child become independent and secure, acquires language, and then begins to learn consciously around age 3. (2) 6-12 years of age the child takes in all aspects of the culture develops imagination, is interested in justice and right and wrong, and adapts to their peer group. (3) 12-18 years of age, the human searches for meaning in life, increases attachment to the peer group and personal relationships, and develops special interests and talents. (4) 18 – adulthood. Takes his/her place in the world, perhaps finds a mate and also develops economic independence. (Montessori, Maria) Each plane has sub-divisions: 3 years of creation and 3 years of crystallization. (Baker, Kay)

"Successive levels of education must correspond to the successive personalities of the child. Our methods are oriented not to any pre-established principles but rather to the inherent characteristics of the different ages. It follows that these characteristics themselves include several levels." (Montessori Maria, From Childhood to Adolescence, p. 1) "If 'the formation of man' becomes the basis of education, then the coordination of all schools from infancy to maturity, from nursery to university, arises as a first necessity: for man is a unity, an individuality that passes through interdependent phases of development. Each preceding phase prepares the one that follows, forms its base, nurtures the energies that urge towards the succeeding period of life. (Montessori Maria, From Childhood to Adolescence, p. 84)