The school environment has the potential to impact Non-Communicable Disease-related behavioural change in children and adolescents. Interventions to advance health literacy in children can encourage healthy eating and have long-term implications later in adulthood. Positive feedback from the participants in the formative study suggests that interactive modules including a short film and follow-up interactive activities can be effective in promoting a healthy lifestyle among children and adolescents in schools. Further evaluation of the intervention using a cluster RCT was useful to assess its effectiveness on knowledge and behaviours related to diet and physical activity of school-going adolescents. The findings indicated a positive effect of the intervention on diet and physical activity-related changes in the expected direction.