The last two decades have seen significant declines in the proportions of high school students choosing senior physics, chemistry or biology courses in Australia. The recently published Choosing Science study attempts to understand factors contributing to these declines. In particular it investigates influences on Year 10 students' decisions about taking science subjects in Year 11, on the basis of large-scale national surveys of Year 10 students and secondary science teachers. The survey results have challenged some commonly held explanations for the declines in enrolments. On the other hand, they highlight the impact of expanded subject choice in post-compulsory schooling. In this new, competitive environment, several long-term factors associated with school science are now working to deter enrolments in these subjects at senior level.