Although the entrance age varies in individual schools, a child can usually enter a Montessori classroom between ages of two and one half and four, depending on when he can be happy and comfortable in a classroom situation. He will begin with simplest exercise based on activities which all children enjoy. The equipment which he uses at three and four will help him to develop concentration, co-ordination and working habits necessary for the more advanced exercises he will perform at five and six. The entire program of learning is purposely structured. Therefore, optimum result cannot be expected either for a child who misses the early years of cycle, or for one who is withdrawn be he finishes the basic material described here.