To understand the relationship between social background and sex in schooling, we use Bourdieu's theory of social reproduction and a feminist perspective of gender as practice. We pose two questions: (1) What is the relationship between economic and cultural capital and achievement for 4th-grade females versus males studying in Germany? (2) Is the relationship between school composition and student achievement different for 4th-grade females versus males? We report no differences between females and males in the relationships between social background and achievement (p > 0.05). However, the relationship between class-aggregated social background and achievement is halved in female-majority mathematics classrooms (β = -12.6, p < 0.05).