Planes of Development

One of the cornerstones of the Montessori educational system is the mixed-age classroom.  Montessori classrooms are broken into age groups that span three years, which teachers often refer to as the “three year cycle.”  But what is the significance of these age groupings?

These age groupings are based on Maria Montessori’s theories of education  She identified four distinct periods in child development, characterized by habits, tendencies, sensitivities and proclivities: ages 0-6, 6-12, 12-18, and 18-24.  Children in each age grouping tend to follow certain patterns with regards to their physical, social, emotional, and cognitive needs.  

The planes of development are represented in the image below, where the gold triangles represent rapid growth and the black triangles represent relative periods of stability.  These two sets of planes parallel each other.  As Angeline Stoll Lillard writes in Montessori: The Science Behind the Genius, “From 0 to 6 the infant is forming into the child, and from 6 to 12 this person consolidates; then from 12 to 18 the child is forming into the adult, and from 18 to 24 this person consolidates.  Thus the young teen, In [Montessori’s] conceptualization, shares many characteristics with the 2 year old, and is in a time of great change.”

Image source: Trillium Montessori

Now you may be thinking, if these planes of development span 6 years, why are classrooms broken into 3 year age groups? Well, Maria Montessori noticed that the first half of each plane (the upward side of each triangle) was characterized by an explosion of new growth, and the second half of each plane (the downward side) was characterized by refinement.  Think of the incredible transformation your child undergoes from birth through three years old: learning to walk, talk, be in control of their body, and explore and engage with the world around them.  The next three years are spent refining these skills: learning to express their thoughts and feelings, listening and understanding those around them, learning to draw and hold a pencil and climb a tree, learning to reason and compare and remember.  Thus, we group classrooms along the three year sub planes: ages 0 to 3 in Nido, ages 3 to 6 in Primary, ages 6 to 9 in Lower Elementary, ages 9 to 12 in Upper Elementary, and so on.  (Nido programs are often further broken into ages 0 to 18 months as an Infant group and ages 18 months to 3 years as a Toddler group).

One of the advantages of grouping classrooms along developmental planes rather than age is that no two children are alike.  Some children take longer to hit certain milestones or develop certain skills than others.  In a mixed-age setting, children are given the freedom and flexibility to grow on their own timeline, with individually tailored guidance and instruction from their teacher, while still being in a classroom of peers.

Another advantage of mixed-age classrooms is the tremendous amount of social learning that happens.  Older children get the opportunity to be leaders, helping them develop skills like confidence, empathy, and communication.  The older children are also often asked to give lessons or to help instruct the younger children– which is actually a technique that helps the older children consolidate their own learning.  Likewise, the youngest children in the class have role models.  They see the big kids as something to aspire to.  They are also exposed to more complex academic concepts by observing the older children’s lessons.  

A more in-depth explanation of each plane of development can be found here, at the blog from Trillium Montessori.  Overall, the planes of development provide a strong framework for Montessori teachers to construct their classrooms and to observe and instruct their students with the individualized, respectful approach of the Montessori method.

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