The belief that children should earn their keep is one of the most significant differences between past and present concepts of childhood. This article examines child labor in Mexico City during the 1920s and 1930s, a period of rapid change in ideas about children's economic and social roles. In the decades following Mexico's revolution, activists in Mexico's child health and protection movement condemned child labor on the grounds that it harmed young workers and led to crime, while a new slate of laws forbade child labor and restricted the kinds of work that adolescents could perform. In contrast, working-class children and adolescents and their parents saw work as integral to family relations. These conflicting views collided in the arena of the juvenile court, one of the principal institutions to emerge from the broad reform agenda focused on children and youth. Yet, while court founders and officials associated child labor with immorality and family dysfunction, the court also provided a forum for working-class children and parents to argue for a different version of family morality founded on long-standing legal definitions of reciprocal obligations of support. Their accounts of children's economic contributions to family subsistence also shed light on the power dynamics entangled in family relationships founded on work. The encounters between court officials and clients illuminate the tensions between state goals and established practices of social reproduction during a profound transition in social views of childhood, the family, and work.