The science curriculum to age 16 should be judged on how well it meets the needs of students who progress to A-level science courses and those (a larger number) who do not. To address the diversity of students' interests and aspirations, we need a clear view of the purposes of science education rooted in a view of the purposes of education itself. This article argues that a flexible curriculum structure for science is essential at key stage 4, offering a variety of pathways that can be better matched to the needs and interests of students.