Infant and toddler programs
Montessori classrooms for children under three fall into several categories, with a number of terms being used. A nido, Italian for "nest", serves a small number of children from around two months to around fourteen months, or when the child is confidently walking. A "Young Child Community" serves a larger number of children from around one year to 2½ or 3 years old. Both environments emphasize materials and activities scaled to the children's size and abilities, opportunities to develop movement, and activities to develop independence. Development of independence in toileting is typically emphasized as well. Some schools also offer "Parent-Infant" classes, in which parents participate with their very young children.
Preschool and kindergarten
Montessori classrooms for children from 2½ or 3 to 6 years old are often called Children's Houses, after Montessori's first school, the Casa dei Bambini in Rome in 1906. This level is also called "Primary". A typical classroom serves 20 to 30 children in mixed-age groups, staffed by fully trained teachers and assistants. Classrooms are usually outfitted with child-sized tables and chairs arranged singly or in small clusters, with classroom materials on child-height shelves throughout the room. Activities are for the most part initially presented by the teacher, after which they may be chosen more or less freely by the children as interest dictates. A teacher's role within a Montessori classroom is to guide and consult students individually by letting each child create their own learning pathway. Classroom materials usually include activities for engaging in practical skills such as pouring and spooning, washing up, scrubbing tables and sweeping. Also materials for the development of the senses, mathematical materials, language materials, music, art and cultural materials, including more science based activities like 'sink and float', Magnetic and Non magnetic and candle and air.
Activities in Children's Houses are typically hands on, tactile materials to teach concepts. For example, to teach writing, students use sandpaper letters. These are letters created by cutting letters out of sandpaper and placing them on wooden blocks. The children then trace these letters with their fingers to learn the shape and sound of each letter. Another example is the use of bead chains to teach math concepts, specifically multiplication. Specifically for multiples of 10, there is one bead that represents one unit, a bar of ten beads put together that represents 1×10, then a flat shape created by fitting 10 of the bars together to represent 10×10, and a cube created by fitting 10 of the flats together to represent 10×10×10. These materials help build a concrete understanding of basic concepts upon which much is built in the later years.
Elementary classrooms
Elementary school classrooms usually serve mixed-age 6- to 9-year-old and 9- to 12-year-old groupings; 6- to 12-year-old groups are also used. Lessons are typically presented to small groups of children, who are then free to follow up with independent work of their own as interest and personal responsibility dictate. Montessori educators give interdisciplinary lessons examining subjects ranging from biology and history to theology, which they refer to as "great lessons." These are typically given near the beginning of the school term and provide the basis for learning throughout the year. The great lessons offer inspiration and open doors to new areas of investigation.
Lessons include work in language, mathematics, history, the sciences, the arts, etc. Student-directed explorations of resources outside the classroom are integral to the education. Montessori used the term "cosmic education" to indicate both the universal scope of lessons to be presented, and the idea that education should help children realize the human role in the interdependent functioning of the universe.
Middle and high school
Montessori education for this level is less well-developed than programs for younger children. Montessori did not establish a teacher training program or a detailed plan of education for adolescents during her lifetime. However, a number of schools have extended their programs for younger children to the middle school and high school levels. In addition, several Montessori organizations have developed teacher training or orientation courses and a loose consensus on the plan of study is emerging. Montessori wrote that, "The essential reform of our plan from this point of view may be defined as follows: during the difficult time of adolescence it is helpful to leave the accustomed environment of the family in town and to go to quiet surroundings in the country, close to nature".
Some Montessori schools for adolescents 12-18 are set in rural locations.