The wide and enduring educational disparities between European and Asian heritage New Zealanders on the one hand, and indigenous Māori and Pacific Islanders on the other, have been a national education policy priority for some time. Such is the degree of focus on ethnic inequalities that very little attention is devoted to sources of privilege and disadvantage related to socio-economic status (SES) and gender, despite international scholarship showing that both of these profoundly influence experiences of schooling. The current study explores the ways in which SES, ethnicity, and gender influence students’ experiences of learning mathematics in New Zealand schools. Mathematics is a ‘gatekeeper’ subject for a range of highly lucrative career pathways dominated by European and Asian heritage men, making access to mathematical success a social justice issue with powerful material consequences. This thesis describes a mixed methods study of 425 Year Nine (age 13-14) students in three New Zealand state secondary schools, which investigated • the relationships between SES, ethnicity, gender, and success in mathematics, • cultural ideas about what types of people have mathematical ability, and • the effect of ability grouping on attainment disparities. European and Asian students had higher mathematics attainment than Māori and Pacific students. Pacific students reported enjoying mathematics despite their low attainment, whereas Māori students had very negative attitudes towards mathematics. Consistent with international studies, girls had lower confidence than boys in their mathematical abilities, despite having equal attainment. Interview data suggested that these differences in perceptions of mathematics were related to cultural ideas of mathematics as a ‘brain’ activity and therefore a natural fit for socially privileged men. Such ideas were further reinforced by ability grouping, which provided successful students with additional enrichment and withheld from low-attaining students the intellectual challenges that could have facilitated a shift to more successful learning trajectories.