After graduating, Montessori worked as an assistant at the psychiatric clinic, where she encountered children with intellectual disabilities. This experience sparked her interest in their education and well-being.

She also volunteered in a Women's asylum, where she encountered young children with mental disabilities who lacked stimulation and education. This solidified her resolve to improve their lives.

Montessori became the director of the State Orthophrenic School of Rome, an institution for children with intellectual disabilities. Here, she began to develop her educational methods, drawing on the works of Itard and Séguin.

Montessori lectured on the education of deficient children, advocating for a scientific approach to pedagogy and highlighting the potential of these children to learn and develop. Her lectures brought attention to the needs of marginalized children.

Montessori began experimenting with sensory materials and educational techniques designed to stimulate the senses and promote learning in children with disabilities. These experiments laid the foundation for her Montessori method.

Montessori returned to her academic pursuits, studying experimental psychology and educational theory at the University of Rome. This period of study further informed her understanding of child development.

Montessori ended her work with children with intellectual disabilities and devoted her attention to applying her educational principles to typically developing children. Her research and observations led to the creation of the Casa dei Bambini (Children's House), a revolutionary approach to early childhood education.