How student teachers experience their transformation into serving teachers in the liminal social spaces of the school-based practicum (teaching practice) is of key importance to them, their future students and their educators. The practicum is a challenging experience for student teachers, even with help from university and school-based mentors, as their knowledge of practice, power and culture in schools lacks sophistication. The practicum, an under-researched but important aspect of education, was investigated by this study by asking 480 student teachers in three universities in Turkey and England in 2010-2011 about how well their universities prepared them for the practicum, what made practicums successful and how practicums fostered their professional development. Participants generally thought the practicum helped them to develop skills in student and classroom management, in meeting students' diverse learning needs, in recognising multiple students' perspectives and in grounding their understanding of what it meant to be a teacher "for real".