Correlational research has shown that experiencing personal relative deprivation is negatively related to adolescents' psychological health and school engagement. Two studies are designed to experimentally test the causal effect of personal versus collective relative deprivation in the classroom context on adolescents' self-esteem and school engagement. In the first study, 211 French eighth-grade students imagined an experience of personal relative deprivation (n = 107) or collective relative deprivation (n = 104) in the classroom and completed a measure of state self-esteem, social and cognitive school engagement, and behavioral disengagement. Findings revealed that the personal relative deprivation condition, rather than the collective relative deprivation condition, decreased state self-esteem and social engagement while increasing the behavioral disengagement of adolescents. The relationship between imagined relative deprivation and state self-esteem was completely mediated by social engagement. In the second study, participants imagined an experience of personal relative deprivation (n = 65), collective relative deprivation (n = 64) or equality (n = 61) in the classroom. Compared to the collective relative deprivation condition or the equality condition, the personal relative deprivation condition reduced perceived control, social engagement, state self-esteem and increased behavioral disengagement. Serial mediation analyses demonstrated that the relationship between the imagined situation and state self-esteem was mediated by perceived control and behavioral disengagement, respectively. Results causally demonstrate the pernicious effects of imagined personal relative deprivation and the benefits of mental imagery based on equal treatment of students on their perceived control, self-esteem and academic engagement. The implications for adolescent classroom management are discussed.