A steady decrease in the levels of physical activity during childhood and adolescents has been noted in various parts of the world. The picture of low physical activity levels in developed countries is no different in developing countries. Children spend the majority of their day at school therefore a school setting is ideal to conduct physical activity intervention studies. The primary aim of this study was to measure the effect of an intervention programme on the physical activity participation patterns among school going children and adolescents. The conveniently selected sample from an urban independent Catholic school included all learners from grade 5 to 7 with parental consent. Baseline data included among others, patterns of physical activity participation, and support for physical activity. Physical activity was assessed with the Modifiable Activity Questionnaire for Adolescents.1 Learners were requested to indicate on how many days of the week preceding the study they participated in vigorous (VPA) and moderate activities for at least 20 min. Support for physical activity from friends and family was also measured.2 The 12-week Promoting Lifestyle activity for Youth (PLAY) programme3 was implemented at the school. Two weeks after the programme, repeat measurement of variables was collected. The mean number of sessions of VPA per week was higher after the intervention programme (3.71 days) than before (3.17 days; p<0.05) and higher levels of support from family for physical activity was reported. The mean number of sessions of moderate physical activity increased with the frequency of family and friends social support. All bivariate correlations between the family and friends social support variables and moderate physical activity were positive and some were statistically significant (p<0.05) The results of the study indicated that intervention programmes such as PLAY have the potential to increase the levels of physical activity participation and support from family for physical activity among learners.