Montessori school teachers educate students using approaches that reflect the Montessori philosophy and principles. They focus on constructivist and "learning through discovery" teaching models, through which they encourage students to learn from first-hand experience rather than through direct instruction and thus provide the students with a relatively high level of freedom. They adhere to a specific curriculum that respects the students' natural, physical, social and psychological development. Montessori school teachers also teach classes with students differing up to three years in age in rather large groups, manage, and evaluate all the students separately according to the Montessori school philosophy.