The evidence discussed in this paper was gathered in a one-year study of how student teachers learn about learning in primary schools. In examining mentoring we pursued three research questions in order to increase our understanding of how mentoring processes were helping student teachers to work responsively in classrooms with pupils. The questions were as follows. What do mentors believe they offer student teachers as they learn to teach in primary school classrooms? What do they offer students? What does the way they support student teachers tell us about how mentors are positioned in the activity systems of their own schools and initial teacher training programmes? The first two questions focus on mentoring as mediation of the knowledge of primary teaching and induction into a community of practice of primary teaching found in each partnership school. The third question takes us to the activity systems in which this mediation occurs. The activity theory analysis allows us to see how mentors can be positioned in their own school and in training partnerships, the dilemmas that ensue from the ambivalence of their position and the implications for the learning of student teachers.