Planes of development
The planes of development are Montessori's division of growing up into four stages, the first three running from birth to 6, 6 to 12 and 12 to 18, each with its own way of learning.
For a homeschool, the line that matters falls between the first and second planes. The moveable alphabet sits right on it. In The Montessori Elementary Material (1917) she says writing and reading are normally in place at five. A child who starts using written words to express their own thinking is ready for elementary work. That readiness, she adds, is a matter of mental maturity, not age.
What the earlier books already said
The 1914 handbook was written for one stage: the child from three to seven, "a formative period of life." The 1912 book splits education into two aims. Helping natural development comes first in these years. Fitting the child to the world around them should get more attention later, once the period of intense development is past.
Notice the ages. The early books treat three to seven as the first stage; the later scheme puts the break at six.
One process, not two schools
The 1917 book insists that the Children's House and the first school grades are "one and the same thing, the continuation of an identical process." Children stayed in the Children's House up to seven, and the 1917 book carries the primary work on into the first grades.
AMI's quotation page gives the later wording. The first phase runs from birth to about six. The next runs from six to twelve, a period of growth without other change. The third runs from twelve to eighteen.
For a family with mixed ages
Plan by plane, not by grade. A four-year-old and a six-year-old can share one morning and one shelf. A nine-year-old needs different work. When a child of five or six writes their own sentences with the moveable alphabet, that is the signal Montessori named for moving on.
Sources
Passage numbers point into the public-domain texts this site checks every citation against.
- The Montessori Method, Maria Montessori (1912), ch. XIV, passage 39863:307: Helping natural development comes first from three to seven; adapting the individual to the environment gets more attention once the period of intense development is past.
- Dr. Montessori's Own Handbook, Maria Montessori (1914), Introduction, passage 29635:10: The method has special reference to the child from three to seven, a formative period of life.
- The Montessori Elementary Material, Maria Montessori (1917), Part I, passage 42869:6: Writing and reading normally established at five; readiness for elementary work a matter of mental maturity; children stayed in the Children's House to seven; the Children's House and the lower grades one continuing process.
- Four Planes of Development (quotations), Association Montessori Internationale (read ): Quotes from Four Planes of Education and The Absorbent Mind: birth to about six, six to twelve, twelve to eighteen.
To see this at work across a whole area, the language lessons list every lesson in order, with its age and materials.
Related terms: sensitive periods, work cycle, prepared environment. All eight are in the glossary.