The introduction of the General Certificate of Secondary Education (GCSE) in 1986 marked a significant shift in music education policy and practice across England, Wales, and Northern Ireland. In comparison to the previous General Certificate of Education (GCE) and Certificate of Secondary Education (CSE) qualifications—which were commonly perceived to be inequitable and inaccessible (Pitts, 2000; Wright, 2002; Rainbow & Cox, 2006)—the GCSE emphasised the central importance of a triumvirate of inclusive, practical skills: performing, composing, and appraising. Forty years later, in a very different educational climate, this tripartite understanding of music remains the epistemological foundation for secondary music education across the three nations, both within and prior to GCSE examinations taken at age 16. Statutory and non-statutory guidance such as England’s National Curriculum and Model Music Curriculum (Department for Education, 2013, 2021), the Curriculum for Wales and Welsh National Plan for Music Education (Welsh Government, 2020, 2022), and the Northern Ireland Curriculum (Council for the Curriculum, Examinations and Assessment, 2007) all employ frameworks of performing-composing-appraising as ‘a blueprint for progression through [...] a sequence of learning across singing, listening, composing and performing’ (Department for Education & Department for Culture, Media and Sport, 2022, p. 23).However, since the earliest debates around the musical epistemology enshrined in the threefold structure of the GCSE, ‘opportunities for public discussion of new ideas [have become] rarer’ (Pitts, 2000, p. 147) and the foreclosing of meaningful policy dialogue has gradually delegitimised ways of knowing that challenge or exceed performing, composing, and appraising. In this paper, we trace this process through the four decades between 1986 and 2026 using historical and documentary evidence from England, Wales, and Northern Ireland. We highlight four emergent trends in educational policy: quiescence resulting from political conflict; divergence of progressive aspirations through national devolution; convergence of practice through neoliberal standardisation; and, finally, coalescence towards neoconservatism. We suggest that while the initial establishment of the GCSE was widely considered a force for progressivism, subsequent political pressures (Lilliedahl, 2023; Young, 2023) have led to a renewed prioritisation of propositional theoretical knowledge, mandatory set works, and abstract assessment outcomes. As the qualification therefore becomes increasingly prescriptively regulated, this insidious shift towards a fourfold epistemological framework of performing-composing-knowing-appraising seems likely to erode the future of the GCSE as the equitable and accessible approach to musical assessment for which it was originally intended.