This paper examines certain controversies among a group of secondary education science teachers with regard to the teacher’s role and his/her professional environment, their views being gathered following a training programme aimed at introducing a key competences approach into the Spanish science curriculum. During the programme they were required to design, implement, and assess their own teaching unit for developing students’ scientific competences by means of context-based learning. At the end of the programme a representative group of teachers were selected to take part in a focus group in which they discussed the training received and its transferability to the classroom. Their statements were then analysed and categorised in order to identify factors associated with their professional environment (at the level of both school and the wider education system) and the implications they had for classroom practice. The present study focuses on those aspects which generated controversy among the teachers, specifically as regards whether they were seen as facilitating or as an obstacle to the teaching of science via a competence-based approach. The issues of controversy related to the following topics: the approach to teaching, the content to be taught, the views of and coordination with colleagues, the utility of contexts and the need for reflection on one’s own practice. The paper concludes by considering potential reasons for these issues of controversy and the implications they have for a competence-based approach to teaching.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.I+D Excelencia project EDU2013-41952-