The structure of aged-based education and the science of childhood development were introduced to China in the last decades of the Qing dynasty. Drawing on period textbooks, journal articles, and school documents for women and children, this study argues that the theory of childhood development helped shape socialized play and citizenship training in new schools. These new institutions followed scientific insights about childhood development in terms of both physical and emotional growth. Educators hoped to found schools that would inculcate respect for political authority within the classroom, and administrators took unprecedented steps in documenting and regulating children. Schools not only became places for disseminating learning, but also centers for gathering information about children and their families, as well as about childhood itself. The production of knowledge and the institutionalization of schools for preschool children helped usher in new trends that denaturalized childrearing outside of the family domain.