In the mandatory, integrative and non-confessional school subject of Religious Education in Sweden, all students are taught together regardless of religious or secular affiliation. The overall aim of this thesis is to explore and analyse how Religious Education (RE) can be socially constructed in the upper secondary school classroom practice in the pluralistic context of contemporary Sweden. The result is based on findings from participant observations of 125 Religious Education lessons at three upper secondary schools in Sweden, both on vocational programs and on preparatory programs for higher education. Discourse analysis, curriculum theory, and didaktik of religion are used as theoretical and analytic approaches. The findings indicate that a secularist discourse was hegemonic in the classroom practice and implied norm of talking about religion, religions and worldviews as something outdated and belonging to history. A non-religious, atheistic position was articulated as neutral and unbiased in relation to the subject matter and was associated with being a rational, critically thinking person. However, there were also spiritual and swedishness discourses of religion that in some respects challenged the hegemonic discourse, but also enforced it. The programs at upper secondary schools were influenced by different educational discourses called a private discourse and an academic rational discourse, which affected the construction of the subject in these different contexts. Implications of the discourses are discussed in relation to the classroom practice and aims of Religious Education.