Instilling values in children is among the cornerstones of every society. There is wide agreement that beyond academic teaching, schools play an important role in shaping schoolchildren’s character, imparting in them values such as curiosity, achievement, benevolence, and citizenship. Despite the importance of this topic, we know very little about whether and how schools affect children’s values. In this large-scale longitudinal study, we examined school principals’ roles in the development of children’s values. We hypothesized that relationships exist between principals’ values and changes in children’s values through the mediating effect of the school climate. To test our predictions, we collected data from 252 school principals, 3,658 teachers, and 49,401 schoolchildren. A multilevel structural-equation-modeling analysis yielded overall support for our hypotheses. These findings contribute to understanding the development of children’s values and the far-reaching impact of leaders’ values. They also demonstrate effects of schools on children beyond those on academic achievement.