Governments across the west have put teachers at the forefront of efforts to tackle radicalisation of young people based on their proximity to potentially vulnerable students. This has proven controversial, as critics claim that this securitises teachers' work and that they cannot be expected to accurately identify and respond to extremism. Despite investment in P/CVE teacher training, research to assess teachers' competence to identify signs of radicalisation and to respond in an appropriate manner is scarce. This article presents findings from a survey experiment with 2,173 teachers in Great Britain and Denmark. It shows that British and Danish teachers largely recognise radicalisation cues and respond to student radicalisation in similar ways. However, our data shows that British teachers are more likely than Danish teachers to react formally (e.g. report to authorities), and that British teachers feel more confident in reacting to signs of radicalisation. The results enhance our understanding of the effects of radicalisation prevention in schools. Furthermore, they challenge arguments within the extant literature by suggesting that what leads to concerns of radicalisation is not entirely subjective or completely context dependent.