The Casa dei Bambini — the Children's House — opened on January 6, 1907, in a tenement in the San Lorenzo district of Rome. The district was among the poorest in the city, and the children placed in Montessori's care were, by every conventional measure, difficult: restless, aggressive, unfocused, resistant to instruction, prone to disruption. Montessori did not punish. She did not lecture. She did not impose behavioral regimes. She prepared an environment with child-sized furniture, provided the materials she had refined during her work with intellectually disabled children, gave the children freedom to choose their own work, and observed. What followed was a transformation so profound she initially doubted her own perception. Children who had been restless became concentrated. Children who had been aggressive became gentle. Children who had been unfocused became absorbed in work for periods far beyond what anyone predicted. The transformation occurred through no mechanism conventional education employed — not instruction, reward, punishment, or coercion. It occurred through engagement with meaningful work in an environment meeting developmental needs. The Casa dei Bambini became the founding experiment of the Montessori method and the empirical basis for every subsequent claim in her framework.
The site was arranged by Edoardo Talamo, director of the Istituto Romano di Beni Stabili, a property management company that had renovated the San Lorenzo tenements and needed a solution for the unsupervised children damaging the hallways while their parents worked. Talamo offered Montessori a single ground-floor room and a small budget. She brought her materials, her child-sized furniture, and her willingness to observe without preconception what happened when children were given the conditions she had been developing.
The observations she made there — of normalization, spontaneous concentration, the emergence of self-discipline without external enforcement, the social harmony that developed among children given meaningful work — became the empirical foundation of her entire subsequent theoretical framework. The absorbent mind, the sensitive periods, the developmental function of the prepared environment — each concept traces back to phenomena first observed at San Lorenzo.
The Casa dei Bambini was also where Montessori first observed that three- and four-year-olds, given access to sandpaper letters and the movable alphabet, spontaneously began reading and writing — an outcome her contemporaries considered developmentally impossible at that age. The observation overturned prevailing assumptions about readiness and demonstrated that standard developmental timelines reflected the limitations of available methods rather than inherent capacities.
The school's success led rapidly to additional Casa dei Bambini openings across Rome and eventually Italy, and by 1912 the method had spread internationally. The original school at Via dei Marsi 58 no longer operates as a Montessori classroom but remains a significant site in the history of twentieth-century education.
Montessori had been developing her materials and observational method throughout her work with intellectually disabled children in the 1890s and early 1900s. The Casa dei Bambini provided her first opportunity to apply the approach to children without cognitive disabilities, and the dramatic results raised the question that would animate the rest of her career: if these methods produced this much development in children previously considered difficult, what did that imply about the conventional education of ordinary children?
Her 1909 book Il Metodo della Pedagogia Scientifica applicato all'educazione infantile nelle Case dei Bambini (translated into English in 1912 as The Montessori Method) documented the experiments and became an international bestseller, translating into dozens of languages and spreading the method across continents within a decade.
The first experimental site was improvised, not founded. A property company's practical problem with unsupervised children created the opportunity. The method's theoretical architecture followed from observations made there.
The children were not selected for aptitude. They came from the poorest district of Rome, from families under every kind of stress. The development Montessori observed was therefore not an artifact of privileged sampling.
The transformation was observational, not interventional. Montessori did not treat or train the children. She prepared conditions and watched. What the children accomplished, they accomplished themselves.
Normalization emerged unplanned. The constellation of concentration, self-discipline, and social harmony was not what Montessori set out to produce. It appeared spontaneously, and her subsequent theoretical work was in large part an attempt to explain what she had seen.
San Lorenzo's success catalyzed global diffusion. Within five years of the first Casa dei Bambini, Montessori schools operated across Europe and North America; within fifteen, her method had reached Asia.