Background: School climate is crucial: its character can affect pupils' academic achievement, teachers' working conditions and the wellbeing of everyone at school. A major concern for teachers is how to prevent and manage disruptive behaviours. Against this backdrop, there is a need for thorough investigation of pupils' perspectives to better understand their perceptions of the climate at their schools and their views about why disruptive behaviours occur. Purpose: In this small-scale, qualitative study, we aimed to contribute to the body of school climate research by exploring pupils' perspectives on school climate, teachers and relationships at school. Method: We conducted an in-depth qualitative analysis, exploring pupils' perspectives on these issues through focus group interviews. Eighteen semi-structured interviews were conducted (n = 104) with grade 1-9 (7- to 15-year-old) pupils from a school in Sweden. The interview guide included questions about sense of safety, relationships at school and in classrooms, and pupils' views of teachers. Constructivist grounded theory was used as the analytical framework. Findings: A recurrent pattern identified in the data was the focus on disruptive behaviours and how these were connected to the pupils' learning environment, sense of safety and teachers. Three core categories were conceptualised from the pupils' perspectives: (a) within-pupil explanations, (b) teaching style explanations and (c) peer group process explanations. We adopted a social-ecological approach to conceptualise the complexities and interplay of factors addressed by the pupils in their perspectives on disruptive behaviours. Conclusions: Our findings provide insight into the way that different factors interplay in the emergence of disruptive behaviours in the classroom, nested within both contextual and structural aspects. This analysis of pupil perspectives also points to the importance of a whole-school approach in which teachers establish a warm, responsive and confident teaching style in the classroom and in the playground to influence the social dynamics.