Bad student behaviour is argued to be one of the major challenges for schools today. In response to the challenge, there is a strong body of literature aiming at fixing student behaviour. In this paper, we look into professional knowledge discourses regarding 'bad student behaviour,' focusing on one national context, Finland, to explore how disturbing behaviour is discursively established in the professional literature for teachers seeking help with challenging student incidents. We analyse expert sources that are readily available for Finnish teachers (n = 19), looking at what fields of science are represented, whose voice is represented, how the problem is defined, and where it is located. We conclude that the professional discourse about disturbing behaviour in Finland places the problem on the individual child or family while also silencing the individuals in question and portraying them as deficient. Furthermore, the sources produce a decontextualised notion of behaviour and describe it as either acceptable or unacceptable, completely overlooking any societal, historical or cultural aspects of behaviour or other mitigating circumstances. The findings resonate with research findings from other international contexts.