This article argues that the concept of rationality is undergoing significant revision in UK education policy-making, influenced by developments in several academic fields. This article focuses on the take up of behavioural economics in policy as one aspect of this revision of the concept of rationality, discussing how this has happened and its implications. Framed by a wider debate regarding the significance of a "crisis" in neoliberal approaches to social change, behavioural economics suggests that a reliance on rational choice is insufficient and individuals need to be "nudged" to make good choices. This revision and its impact on the subject of policy, the policy-maker and policy technologies are examined, and the discussion is supported by two illustrations from school choice and youth service policy texts from the 2000s. The potential use of "nudge" theory in education is also considered with respect to the Conservative-Liberal Democrat government's use of behavioural economics. In conclusion, we argue that the use of these ideas in policy, alongside others, marks a revision of the neoliberal idea of a rational chooser as the aim of policy-making, of which education policy sociology should take account. (Contains 6 notes.)