The aim of the study was to investigate the relationships of classmate and teacher support during physical education (PE) lessons on moderate-to-vigorous physical activity of 14-16 year-old students whom were underweight, normal weight and overweight. The cross-sectional sample for the study concerned data from 1702 girls and 1547 boys, recruited from 12 junior high schools in Poznan, Poland. Based on their body mass index (BMI) values, the participants were assigned to weight categories: underweight, normal weight and overweight. We determined the levels of physical activity, and teacher and classmate support, by means of a questionnaire-based survey. The 3-way interaction effect of gender, weight and support from teachers was statistically significant ("p" = 0.05); the 3-way interaction effect of gender, weight status and support from classmates approached significance (p = 0.0526). This research concluded that supporting students during the PE process may play an important role in determining one's level of physical activity.