Teacher education programmes offer pre-service teachers limited opportunities to realistically practise and develop skills and strategies for teaching pupils, without the risk of adversely affecting pupils' learning. The purpose of this study was set to contribute with knowledge concerning how pre-service teachers develop self-efficacy beliefs from different sorts of teacher training. Three sorts of experience -- teaching virtual characters, teaching peers and teaching pupils in schools -- were compared. The results show that three hours of simulation training in a small group setting with virtual characters develops pre-service teachers' self-efficacy beliefs in teaching mathematics just as much as three weeks of training with real students and significantly more than teaching colleagues during a seminar. The pre-service students especially mentioned the feedback from the instructors as being valuable for creating an efficient professional learning environment, with respect to development of teaching efficacy beliefs.