The training of teaching assistants in the UK is undergoing considerable change linked to workforce reform in primary schools. This article examines the role that class teachers play as mentors in the training of teaching assistants on two types of programmes operating in England leading to Higher Level Teaching Assistant Professional Status. It considers the qualities required for mentoring teaching assistants compared to mentoring trainee teachers. The views and perspectives of a group of thirty-four school teachers who have carried out a mentor role for both a trainee primary teacher and a primary teaching assistant are analysed. The research aims to identify the common skills, strategies and approaches used by the school-based mentors and identify the perceived tensions and challenges facing these mentors. [Appended to this document is "Questionnaires to mentors (respondents N = 34)."]