Sociologists have long noted that childrearing shapes young people's life chances. Worldwide, rural‐to‐urban migration is growing, yet we know little about whether or how migrants adopt new childrearing beliefs during this rapid social transformation. Using interviews with 63 parents and ethnographic observation at a public school, I examine how rural‐to‐urban migration affects the childrearing beliefs of indigenous peasants who move to the city of El Alto, Bolivia. Many migrants reject rural childrearing's reliance on corporal punishment and limited verbal communication, instead embracing more open communication, limited physical punishment, and parent–child trust. Urban organizations and social ties expose parents to a new childrearing model, and parents find this model credible when they observe that it buffers children from urban dangers that threaten young people's mobility chances. Adopting urban childrearing ultimately entails accepting an underlying model of children's agency, wherein children need internal motivation instead of external impulsion. This case shows that individuals’ childrearing beliefs are more malleable than previous sociological studies suggest. I close with policy implications for parental education and child well‐being initiatives.