How do multi-age classrooms help Montessori students develop social skills?

Maria Montessori’s theory of child development was based on a three-year cycle. Therefore, 3- 4- and 5-year-olds are grouped in the Primary program, 6- to 9-year-olds make up the Lower Elementary program, and 9- to 11-year-olds are in the Upper Elementary Program.
The multi-age setting allows children to learn FROM each other, as well as BECAUSE of each other. Older children reinforce their knowledge by teaching younger ones, and younger ones get a preview of what’s to come by watching older students. Children also learn to get along with people of different ages and abilities, to respect each other, and to treat each other with courtesy. When a child masters a project, they may be invited by the teacher show their accomplishment to older students. It is not unusual to overhear a 6-year-old sincerely telling an even younger student, “You did a great job!”