The study of higher-level secondary mathematics is considered essential for national economic growth, competitiveness in research and innovation, and further education opportunities. Yet the reported trend within Australian secondary schools is that enrolments in higher-level mathematics are declining and have been in a state of decline for over a decade. The little available and recent literature published on this phenomenon has looked at why secondary students elect to study higher-level mathematics courses, both from the perspective of teachers and students. This research paper presents findings as to why Heads of Learning Area: Mathematics (HOLAMs) believe capable secondary students elect not to enrol in those courses. Data were collected from 50 secondary schools across the three sectors (Government, Catholic, Independent) in Western Australia. The key findings are that capable students do not enrol in higher-level mathematics courses because these courses are not required for university entrance, other courses appear to be less rigorous and more viable, and the Australian Tertiary Admissions Ranking (ATAR) score can be maximised by taking one mathematics course instead of two courses.