This article studies content issues by examining teachers’ communicated socialization content. The value-laden socialization content constitutes the educational context for the teaching of integrated subject matter and has not yet been thoroughly studied empirically in environmental education research. The implications of the results can be fruitful in discussions about how educational traditions evolve, as well as discussions about the relationships between environmental education and education for sustainable development. In this study, ten upper secondary teachers are interviewed and their expressed socialization content is examined. Various qualitative positions regarding five important educational aspects can be described in terms of three selective traditions. To strengthen the validity of the socialization content found in this study, the students of the same teachers were interviewed regarding their experiences of the socialization content of these teachers’ teaching. This is reported in a supplementary article (Sund & Wickman, this issue). Together these three studies (this article, Sund & Wickman, this issue and Sund, 2008) work to establish and test a method of discerning qualitative aspects in socialization content. Although the amount of data is limited, the ambition has been to triangulate socialization content qualitatively from three different sources: a literature study, teacher interviews and student interviews.