At the start of the twentieth century, Dr. Maria Montessori, an Italian physician and educator, began working with mentally disabled children and saw them thrive when given purposeful tasks and treated with respect. In 1907 she opened a day care center in Rome and continued to develop techniques and learning tools that would allow children to take control of their education and progress at their own developmental pace. Thousands of schools all over the world now adhere to Montessori's teachings, and while these schools tend to be private, and most commonly accept children between the ages of 3 and 12, many are public or charter schools and include children as young as 18 months and as old as 18 years.

Typical Montessori classrooms consist of 30 or more students and span three grade-levels, so that one class contains children aged three through six while another holds children aged six through nine and so on. One or two specially-trained Montessori teachers oversees each class along with one or two aids, and each child stays with the same teachers for three years before moving on to the next level. This set-up allows the children and their teachers to form a close and supportive community while also providing other educational benefits. Because they can observe the same students for three years, Montessori teachers gain a more in-depth understanding of each child's strengths, weaknesses, and interests. At the same time, the children do not feel pressured to learn at a faster or slower pace, as the classroom consists of a range of developmental levels. The teachers do not lecture or give lessons to the group as a whole. Rather, they act as observers and guides, introducing children to subjects individually or in small groups and helping them to choose activities that will best support their unique needs and interests. They also encourage the children to teach each other and know that a child has mastered a concept or skill when they can teach it to a peer.

The classroom setting of a Montessori school is often described as a "prepared environment," a term evocative of a central theme in Dr. Montessori's theories, that an appropriate setting can promote children's independence and instill in them a love of learning. The classroom may contain mats for the children to lie on or tables and chairs, but there are no desks, and the children can move about freely, touching, interacting, and exploring. Several areas of the classroom are dedicated to specific areas of study, including language arts, math, history, science, art, music, and practical life skills. Rather than learning from text books, the children learn from educational tools, which are known as Montessori materials and teach a particular skill or concept. These materials, which may take the form of puzzles, games, or tasks, are designed to be self-correcting, so that the child can recognize and fix a mistake without needing help from an adult. The Montessori Method places emphasis on self-directed education, and while older children must meet some requirements, the children are free to choose the topics they want to study and dedicate as much time as they like to each activity. As a show of respect for the child's work, no one is allowed to disturb a child who is concentrating.

Children attending Montessori schools have access to subjects not normally covered until high school, and because students have the freedom to study topics that interest them as comprehensively as they wish, many children reach high academic achievements. Unlike traditional schools, children do not receive grades, though their teachers test them on an individual basis and evaluate their progress, describing their strengths and weaknesses. With an emphasis on active, hands-on learning, mastery of skills, and independent thought, the Montessori Method strives to help children progress as their own pace, develop their own interests, and achieve academic success.