The aim of the present research is to investigate the degree to which average academic outcomes in secondary school classes are associated with the inclusion of markedly disruptive pupils. Findings are based on two separate studies among pupils in Norwegian secondary schools. The first study included a relatively large sample of 2,332 pupils from 105 school classes and used pupil report of disruptive behaviour, perceived peace to learn and grades achieved. A second study, conducted among a smaller sample of 496 pupils from 21 school classes, included teacher reports of pupil behaviour and grades achieved, as well as scores from tests in two school subjects. Results indicate that a relatively large percentage of Norwegian secondary pupils want less classroom disruption. Pupils in classes with markedly disruptive pupils reported significantly less opportunity to learn in peace. However, the percentage of between class variance in perceived peace to learn was relatively low, indicating that lack of peace to learn is a general problem in Norwegian classrooms, irrespective of whether there are markedly disruptive individuals in the class. Finally, academic outcomes were not found to be significantly lower among pupils in classes with markedly disruptive pupils.