This study explored Viennese teachers' ideas about religious diversity in schools. School teachers from three different school districts were interviewed about their attitudes towards having religious diversity in their classrooms and about their experiences with it. The aim was to explore reflections on the recent discussion about religious diversity in Austrian schools. The study showed that teachers reduce religious diversity to the presence of Muslim pupils in their classrooms. In addition, religious diversity is regarded as a source of tension, challenge, and restlessness. They further relate Christianity to secular norms. For many, having various religions in schools is not seen as an enrichment, but a hindrance to creating unity in schools and society. Islam is perceived also as a deterrent for school-parent cooperation, integration, and German learning, while religion-based Muslim peer groups are seen as undesired social groups.