Child-on-child harmful sexual behaviour at school is highlighted in the literature although very little is known about how teachers experience it. Interpretative Phenomenological Analysis was used to address this gap. Semi structured interviews were conducted with nine teachers from two special schools and one mainstream school. Overarching themes used the proverb of the three wise monkeys as a framework in which to show how HSB was not seen, heard or spoken about. Instead, it was accepted and expected as part of the special school day because it was not recognised and paid little attention to, whilst in the mainstream school it was not recognised due to lack of knowledge and understanding. A lack of training, support and the sharing of information compounded teachers' fears for personal safety, careers and reputation. Implications for teachers and multi-agency professionals are discussed.