This study use the theory of community of practice and the theory of mediating tools to explore how teachers develop student’s writing in the Swedish subject in Swedish upper secondary school. The aim of the study is to display the potential to learn and develop writing through participating in the community of practice that is the classroom, as well as with the help of mediational means in the classroom and in other contexts. Five teachers are interviewed on their ideas about teaching students to develop writing. Results from the study show potential for learning through communities of practice and mediational means in the teachers’ use of collaborative writing and interaction between students as well as their aspiration to connect school writing with writing in other contexts. The way in wich some teacher’s switch from collaborative and interactive work forms to individual, when the student’s texts are to be assessed and graded, could on the other hand be considered problematic. The results also imply that the teachers’ choices and positions must be understood in relation to ideas on writing expressed by the students and in the curriculum and in national writing tests.