This article traces the conceptual, legal, and institutional development of Korean “houses of moral suasion” by exploring the example of the first such institution, the Yŏnghŭng School, founded in 1923. The appearance of houses of moral suasion in this era showcases the institutionalization of children deemed problematic and thus undesirable. The idea of rescuing and disciplining children became interconnected and conflated as these children were conceived of as both victims and threats, a process of othering that defined them as simultaneously needy and problematic. In dealing with children, social work aimed to be both disciplinary and protective, and the discourse surrounding the institutionalization of vulnerable children demonstrated the methods through which Korean society criminalized, disciplined, and corrected marginalized children. The link between vagrant or orphaned children and delinquency can be read as a fundamental reordering of the relationship between modern disciplinary power and marginalized children. This in turn reinforced the regulatory approach to undesirable children more generally in colonial Korea.