Sex education can be described as an important part of health education in school and one way of strengthening health education could be a collaboration between different professionals in the school team. The aim of this study was to describe teachers' and school nurses' experiences and perspectives with regard to sex education among students aged 11-12 years and to explore potential influencing factors. We employed a qualitative design, and the teachers and school nurses were interviewed individually. A thematic analysis was conducted on the interviews and the results showed that the classroom was considered to be the teacher's arena. Tradition and attitudes between professionals could be obstacles that affect collaboration between teachers and nurses and the study showed that there remains much to be done before collaboration at the same level between the groups can be established.