The Montessori materials were developed over several years by observing children and ascertaining their needs and their unique ways of
learning. Once Dr. Montessori started on this path, she continued to people begin programs. While the majority of Montessori schools are still
for the 3 to 6 year-old range, Montessori and her collaborators also developed theory, methodology and materials for ages 0-3 and 6-12.
While Montessori did not completely develop the method for students older than 12, the basic philosophy was outlined in her books, and
Montessorians today are increasingly organizing programs for adolescent students. For more information on Maria Montessori's life and work,
we recommend
Rita Kramer's biography.
Other sources: From Wikipedia, the free encyclopedia
Montessori History

Maria Montessori  (1870–1952) was the first woman physician in Italy in the early 1900's. In her practice of medicine, she was called upon to
look after a group of mentally handicapped children. Concerned that they had little to do, she began developing materials for them, and in a
short time they achieved the same skills and knowledge as normal children. This caused her to wonder what all children could achieve if
provided with materials that suited their developmental needs, and it led to a movement that has revolutionized education for children around
the world.