Completion of higher-level mathematics courses in secondary school is advantageous for success in many university-level science, technology, engineering and mathematics courses. Based on survey data from 942 Year 10 students from Western Australia, the Year 11 mathematics course choices made by girls and boys were compared. Findings indicated that girls, and especially high-achieving girls, were more likely than boys to pursue mathematics courses at a lower level than their teachers considered they were capable of completing successfully. Findings also indicated that while both boys and girls were most influenced by teachers and parents in making mathematics course choices, older siblings and older students were more influential on girls than on boys. In general, students who chose mathematics courses of lesser challenge than their teachers recommended reported being less influenced by teachers and the media than others. Findings highlight potential sociocultural pathways through which changes in enrolment patterns may be encouraged.