<p>It has long been recognized that mathematical ability is strongly associated with an individual’s educational and career success. At the same time, studies show significant inequalities in mathematical proficiency levels depending on student characteristics such as sex, socioeconomic status, and migrant background, as well as task characteristics such as language complexity. We applied an intersectional approach to investigate whether the above student characteristics have a multiplicative effect in their relationship with the level of Austrian students’ mathematical proficiency (in general and in specific areas). We also aimed to identify differing effects regarding migrant background in relation to the language complexity of mathematics tasks. The methodological basis for this part of our study is a relatively new data analysis approach developed specifically for the assessment of intersectional effects, the multilevel analysis of individual heterogeneity and discriminatory accuracy. The sample for our analyses was 65,893 8th-grade students in Austria. The main findings of our study confirm already well-known general patterns in how mathematical ability, sex, socioeconomic status, and migrant background are related. However, we could not confirm an intersectional effect of the combination of these characteristics or a different pattern of association between migrant background and specific mathematical abilities differing in language complexity. Our conclusions and recommendations focus on political measures addressing the additive effects of socioeconomic status and migrant background. Regarding sex, measures should refrain from focusing on abilities per se but rather concentrate on so-called non-academic characteristics (e.g., interest and self-concept) that may affect later choices in upper secondary education.</p>