After her training in science and medicine, Dr. Montessori developed her educational practices scientifically, through observation and experiment. She noticed that children of different ages had different needs and tendencies, and determined that therefore the methods and practices of education should change with the children.
The Post Oak School offers five different levels of education:
Since the child's body and mind are different in each of these age groups, the specific educational methods differ as well. But any visitor will see some common, consistent features across the curriculum.
Montessori schools have multi-age classrooms, generally encompassing a three-year age span. Older students teach younger students, both through modeling and through active assistance with lessons and work; both sides benefit, both academically and socially. Young Children's Community and Primary classrooms (ages 0–6) generally involve much more one-on-one focus with the teacher, in keeping with the more solitary, ego-driven explorations that characterize the first plane. By the Elementary (6–12 years old), a grouping instinct has taken hold, and classroom activities actively encourage cooperative work.
Freedom of movement and free choice of activities are important features in any Montessori classroom: rather than sitting in even rows with everyone focused on a single activity, students will disperse to group tables and work on a variety of activities simultaneously, with the teacher observing or moving among them. Freedom is not an absolute; students who do not show enough self-discipline to meet social or academic expectations may find their freedom curtailed until they show more responsibility.
The Montessori curriculum is both wide and deep, offering a wealth of knowledge in the detail desired by each individual, with a unified presentation of knowledge across the age groups and curriculum. A constant goal in the classroom is to plant the seeds for future ideas and activities: one concept is carefully laid in place to aid the comprehension of another, whether months or years down the line. For instance, the Binomial Cube in Primary has as its immediate purpose the development of manual dexterity and pattern recognition—but the same educational material also lays the groundwork for the young adult's understanding of how to cube the sum of two algebraic variables, (a+b)3.
The term "Montessori" was never trademarked; any school can claim to make use of the educational method. Two main groups train teachers and accredit schools in the United States: the Association Montessori Internationale (AMI), founded by Dr. Montessori herself and directed from the Netherlands (with a national branch office in Rochester, New York), and the American Montessori Society (AMS), headquartered in New York City.
AMI teacher training is rigorous: the course requires either a full academic year or three summers, and culminates in the inspection of student-written teaching albums and several days of oral and written exams. AMI offers diplomas for Assistants to Infancy and for Primary and Elementary teachers; only a limited number complete the training each year, and are in high demand around the country and the world.