Purpose: This study seeks to gain an understanding of the complexities involved in real-life classroom teaching. The aim is to trace values and tensions displayed in what the teachers regard as successful and unsuccessful. Design/methodology/approach: Teachers were interviewed to explore their perceptions of success and failures in their teaching about controversial issues. Data was analysed thematically and cross-analysed to find underlying didactic values and tensions. Findings: Successful and unsuccessful are mainly related to the students' learning, teachers' efforts, and reactions of parents, not to specific issues. Values included concern for students' wellbeing and a desire for less polarisation. Tensions concerned students' level of commitment and how to deal with students' own opinions. Successful teaching is not only about achieving curriculum goals but also must be understood in relation to teachers' task perceptions. Practical implications: Results of the study can provide teachers with a ground for didactical reflection.