This study focuses on 20 mentoring pairs in an Israeli teacher training program in order to determine in which ways matched and mismatched expectations of the role of the cooperating teacher between student teachers and cooperating teachers contribute to different opportunities for learning to teach. Perceptions of learning reported in student teachers' pedagogical journals were analysed according to two category systems based on different orientations to teaching and the concepts of support and challenge, and compared to the initial expectations of the cooperating teachers and the student teachers. We found that matched expectations between student teachers and cooperating teachers explained a high degree of support in student teachers' perceptions of learning to teach, whereas mismatched expectations explained a high degree of challenge. We also found a third pattern of expectations that was neither matched nor mismatched, but mixed, in terms of support and challenge in a wide range of orientations to teaching. The conclusion of this study is that the mixed pattern provides opportunities for optimal learning. Based on the findings, we make some recommendations for supervision of participants of mentoring relationships in practicum programmes.