Despite its simplicity and efficacy, the promotion of hand washing for disease prevention remains a challenge particularly in resource-limited settings. Here we report on a quasi-experimental school-based study that aimed to improve habitual hand washing. Significant increases in hand washing occurred following improvements in hygiene and sanitation facilities (School A: t=13.86, p=0.0052). Smaller increases in hand washing occurred following education (School A: t=2.63; p=0.012; School B, no infrastructure improvements: t=1.66, p=0.239). Health policy and programming need to pay greater attention to the interplay of the structural, social, and individual dimensions of unique contextual environments that influence habitual behaviours.