The 1997–2010 UK government's priorities for education and improved social equality led to the development of two major school building programmes: the Academies programme and Building Schools for the Future (BSF). Political concerns for social, economic and environmental sustainability were increasing during the same period, leading to stated new aspirations from 2004 for the schools to be ‘models of sustainable development’. The key political discourses for ‘sustainable schools’ during this era are examined. While some aspects of the initial focus on social equity were retained, there was a rapid shift in emphasis towards environmental sustainability, and specifically carbon reduction. The impacts of these shifting discourses are then considered on four school building projects, examining the technical decisions made and their intended and unintended consequences. Within the diversity and complexity of individual building projects, the paper also exposes both the changing priorities within the construction sector during this period and the impacts of some specific policy tools. The considerable interpretive flexibility in the implementation of the policies is demonstrated, along with variability in their outcomes. Built environment policy should be understood as a continuous process that shapes and reshapes what happens.