The Whitby School was founded in 1958 as a day school for children between the ages of three through fourteen. The founders, a group of Roman Catholic parents, sought to create a lay-directed, co-educational school "organized to teach and educated children, and to conduct and maintain a school for children utilizing the method of education know as the "Montessori Method." This was at a time when Maria Montessori’s ideas about education were being re-examined in the United States. Whitby’s founding head, Nancy Rambusch, was the driving force behind the resurgence of interest in Montessori education. Through that interest Whitby was founded as the First American Montessori School in the United States.

Significant in the history of Whitby, is the early formation of the American Montessori Society in Greenwich, Connecticut. The first teacher training courses, based in Greenwich, used Whitby classes as a lab school. Although training courses are no longer held in Greenwich, Whitby continues to accept intern teachers, and thus contributes to the growth of the American Montessori Society, in which it plays a leadership role.