<p>Despite research consistently showing that social class is associated with academic achievement, there has been limited attention to adolescents’ experiences with social class discrimination and its links to academic achievement. To address this knowledge gap, we conducted a cross-sectional study with 1558 adolescents (40.18% cisgender girls; aged 13–18 years, <i>M</i>_age = 16.17). Two measures of social class discrimination were included: an adapted scale and a measure that addressed multiple sources of social class discrimination. Hierarchical regression analyses indicated that both measures of social class discrimination were negatively associated with academic achievement, even after controlling for social class. Multiple sources of social class discrimination, including teachers, classmates, teenagers, friends, and community members were associated with academic achievement. Teacher-based social class discrimination had the largest effect. Age and gender moderated these associations indicating that the association between social class discrimination and academic achievement was stronger for younger adolescents and girls. Findings highlight social class discrimination as a critical factor contributing to academic outcomes among adolescents.</p>