This article reports on data from a large-scale study investigating students' mathematical transitions to higher education. Three hundred and seventy-one undergraduate bioscientists were surveyed in order to investigate their perceptions and experiences of studying post-compulsory mathematics, as preparation for the mathematics elements of their degree. A-level Mathematics was well-received, with more than three-quarters of participants describing the qualification as good preparation for their degree. Participants particularly valued the statistics units at A-level. However, A-level Further Mathematics was perceived to be less useful preparation, although participants reported that it was enjoyable and challenging. Ongoing qualification reform, as well as the proliferation of post-compulsory mathematics options, means that universities and schools would do well to consider how best to maximise bioscience students' mathematical preparation prior to beginning their undergraduate studies.