Schools can be a place of both love and of cruelty. We examined one type of cruelty that occurs in the school context: sadism, that is, harming others for pleasure. Primarily, we proposed and tested whether boredom plays a crucial role in the emergence of sadistic actions at school. In two well-powered studies (N = 1038; student age range = 10-18 years) using both self- and peer-reports of students' boredom levels and their sadistic tendencies, we first document that sadistic behavior occurs at school, although at a low level. We further show that those students who are more often bored at school are more likely to engage in sadistic actions (overall r = .36, 95% CI [0.24, 0.49]). In sum, the present work contributes to a better understanding of sadism in schools and points to boredom as one potential motivator. We discuss how reducing boredom might help to prevent sadistic tendencies at schools.