Despite decades of attention to gender and school mathematics, gender inequalities in participation persist. This paper uses the lens of gender monoglossia to explore how accounts of gender and mathematics differ in three international contexts: Finland, Australia, and New Zealand. Drawing on data from completed studies, we examine normalised performances of masculinity in relation to location, race, and class, and who these constructions exclude from mathematics. In contrast to previous studies documenting masculine advantages, we note some boys ‘on the margins’ of mathematics in each context. We argue that masculine advantages in mathematics are not universal and that attention to contextual differences in gender monoglossia offers a way to ‘open mathematics up’ by exposing the constructed nature of gender norms.