The UK has emerged as an influential global player in developing policy to counter violent extremism, and therefore it is important to consider the emerging evidence about the impact of this policy in education. The Prevent duty came into force in the UK in 2015, placing a legal responsibility on schools and teachers to implement anti‐terrorist legislation and prevent young people from being drawn into extremism or radicalisation. This article reviews all of the material based on empirical studies in England involving school teachers and students published between 2015 (when the duty was introduced) and the beginning of 2019 (27 articles and reports in total), to consider the impact of the policy on schools. The key themes emerging from our analysis of this evidence base are related to (1) the ways the policy is interpreted within Islamophobic discourses, (2) the emergence of Britishness as a key feature of fundamental British values and (3) the implications of framing Prevent as a safeguarding issue. We argue that the evidence gives support to those who have been critical of the Prevent duty in schools, and that it seems to be generating a number of unintended and negative side‐effects. However, the evidence also illustrates how teachers have agency in relation to the policy, and may thus be able to enact the policy in ways which reduce some of the most harmful effects.