The mixed age class is a cornerstone of the Montessori system of education at every level, as well as part of the secret to its success. Dr. Montessori observed early in her work that children learn not only from their teacher but also from their interactions with their peers. Learning in the Montessori setting is seen as a highly social activity. The Mixed- Age class allows the younger children to learn from the experiences and to inherit the class culture from their older peers, while it allows the older children to gain the experience of being leaders in the classroom.
At all levels of learning, the three year mixed age group community is a fundamental characteristic of the Montessori classroom. Dr. Montessori divided children into these groups based on her research that showed distinct periods of cognitive development, each with its own specific needs and behaviours. In a mixed-age group setting (ages 0-3, 3-6- 6-9, 9-12), there are children at the beginning, middle, and end of each plane of development. From a young age, a child gets to continually experience being a learner, an observer, and a mentor. These learning environments are meant to mimic the family or workplace environment, where members are different ages, have diverse skill sets, and varying needs. As any parent of more than one child can attest, there is a great contrast between the capacities of a six year old and a nine year old. This is one of the reasons Montessori classrooms can accommodate large numbers of children with two guiding teachers: all the students are helping each other, in one way or another.
The interactions and positive communication also benefits all of the children; older students exercise patience, compassion, and empathy through their language, while the younger ones listen and engage in higher levels of conversations than they are currently capable of. Social interactions between peers involve kindness and grace.