The purpose of the article is twofold. Firstly, the ambition is to argue on a theoretical basis, with exemplification in three school subjects in Sweden - religious education, psychology and social studies, for a widening of the understanding of the citizenship education assignment of schools and subject teaching and the point in doing so. Secondly, the ambition is to show what this can mean specifically in relation to the subject teaching of these three school subjects in Swedish primary school and in upper secondary school. The starting point in the argumentation is taken from Hannah Arendt's thoughts on education, man and existence (2004, 1958/2013). The argument leads to the notion that the citizen-forming task of subject teaching not only needs to include agency dimensions - students' 'doing', their opportunities for action and readiness for action in society and in the world - but also existential dimensions - students' 'being in society and the world', their opportunities to grow as unique people in the meeting with subject teaching. As agency dimensions seem to be more elaborated in current subject didactic research than existential dimensions, the ambition in the article is to elaborate in an in-depth manner how existential dimensions can be depicted and the importance of them.