Safe space, used in educational settings as a metaphor, stresses the importance of the classroom being a learning environment characterised by respect and safety. Based on examples from Swedish and Norwegian classroom research, this article problematises and discusses the complexity in the discourse on safe space by asking the critical questions: Being safe from what? -- and safe for whom? Related to the concept of safe space are questions about what possibly can make the classroom an unsafe place. In addition to various types of intimidation, harassment and attacks, discussions about certain issues and topics can, for various reasons, be perceived as threatening. The school is part of society, and in an increasingly polarised climate, controversial issues in contemporary society will often be perceived as controversial in classroom practice. In this sense, instead of giving students false promises of being safe in the Religious Education (RE) classroom, the concept 'classroom of disagreement' may be a useful metaphor, since it makes it explicitly clear that disagreements exist and are part of life.