The purpose of this study was to examine the impact of a 30-minute physical activity (PA) session on Year Two students’ subsequent classroom behaviour. Forty-eight students from three Year Two classes at a NSW private school participated in the study. The number of disciplinary comments directed by the class teacher to individual students (Individual Disciplinary Corrections, IDC) and the class as a whole (General Disciplinary Corrections, GDC) were recorded during a 30-minute lesson with and without previous PA. Subsequent to PA, there were 40% fewer IDCs (p=0.008) and 59% fewer GDCs (p=0.003), amounting to a 49% overall reduction in disciplinary corrections (p = 0.012). The PA session had a positive effect on the Year Two students’ classroom on-task behaviour, as measured by a reduction in disciplinary corrections directed by the class teacher. These findings highlight the potential value of physical activity as a strategy for increasing student classroom on-task behaviour.