We investigate the effects of 'lecture-based' (LBT) – i.e. individual work and rote learning - versus 'discussion-based' (DBT) – i.e. participative and focused on student-centred learning - teaching styles on the test scores and socio-economic inequality of middle-school students randomly assigned to classes using data from the China Education Panel Survey (CEPS) - a large-scale nationally representative survey. Estimates from Unconditional Quantile Regressions and decompositions based on the Recentered Influence Function suggest that LBT raises scores in mathematics, but the effect is non-linear, as students in the bottom and top quintiles are more likely to benefit from it. In contrast, LBT lowers scores in Chinese and English. LBT also has greater influence on socio-economically advantaged students, resulting in larger inequality within classrooms, especially between top and median students. These effects arise under various robustness checks, implying that: (i) teaching styles affect scores and classroom inequality, and (ii) they appear to be subject-specific. These results suggest that teaching styles can be used as a tool to influence students' academic performance as well as the socio-economic heterogeneity that they bring to their classrooms.