The Montessori classroom offers over 500 unique self-teaching materials. These materials accommodate many levels of ability. They are not "teaching aids" in the traditional sense, because their goal is not the external one of teaching children skills or imparting knowledge through "correct usage." Rather, their goal is an internal one of aiding children's mental development and self-construction.

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They aid this growth by providing stimuli that captures children's attention and initiating a natural form of concentration. Children then use the apparatus to develop coordination, attention to details, and good work habits. When the environment offers materials that stimulate children, the teacher is then able to give them the freedom needed for healthy development.