Maria Montessori organized schools with the idea of a learning process in cycles of six years in children as they grow up. This idea was based on her observation of developmental regularities among children. These six years can be divided into two three year periods. This principle does not always coincide with the educational system that countries use, but the three year cycle is dominant in most Montessori primary schools. It means that children of three age groups are in the same class, thereby offering the opportunity of learning from one another. In a Montessori group children belong the first year to the youngest group; the second year they form a middle group and then they proceed to the position of being the oldest children in the class.