The research reported in this article contributes new understandings of systemic change by studying the form of system redesign known in England as academisation. The data illuminate tensions within the neoliberal policy complex that are surfaced in a single secondary school. Although several studies have described academy conversions retrospectively, there has been little research that both analyses the complex month-by-month realities of decision-making and investigates the changing views of policy actors. Drawing on data from documents, observations and interviews, we argue for academisation to be understood, not as a policy or a complex of policies, but as system redesign. Academisation is not simply a legal process: a school can be academised without officially becoming an academy. The new knowledge from this research speaks to a global audience, because the political, economic and cultural processes on which it reports are under scrutiny in other systems with experiments in school autonomy as a form of publicly funded but ‘independent’ schooling.