This paper outlines some of the implications of counterterrorist legislation, including Prevent, for the pedagogical relationship and for educational institutions. The concept of "radicalisation", central to the Prevent Strategy, is one that is contested in the field of counterterrorism, yet educators are now expected to identify and refer students "at risk of radicalisation". Such students are described as vulnerable throughout the policy documentation; however, the way in which vulnerability is conceptualised is resonant with colonial discourses of contagion and immunity, and it risks silencing and even pathologising the person labelled vulnerable. Prevent does not clearly define central concepts such as extremism, radicalisation, vulnerability, and this may make both students and staff fearful speaking freely in classrooms and lecture halls. Based on the experience of teaching IRA and INLA prisoners in the Republic of Ireland, the author outlines a set of philosophical and ethical principles that ought to underpin education. It is argued that education must not be subordinated to security and intelligence agendas on pragmatic, educational and ethical grounds.