The literature on WASH and school re-opening during the COVID-19 pandemic is dominated by guidelines with little in the way of recent evidence or lessons learned. Analysis of data from school re-openings at the end of 2020 suggests that with mitigation measures in place community infection rates should not be affected by children returning to school. Although children carry a lower risk of infection, they do have large numbers of contact in the school environment, so hygiene and distancing measures are important. The key guidelines for WASH in schools during the COVID-19 pandemic include: children and all school staff must be educated with regards to hand hygiene; hand hygiene stations must be provided at entrances and exits; hand washing must be frequent and requires sufficient water and soap; school buses should have hand hygiene measures in place; and the school environment must be disinfected daily. Environmental, or nudge-based, cues are recommended to support behaviour change in children based on pre-COVID-19 evidence. Examples include colourful footprints leading to a handwashing facility, images of eyes above handwashing facilities, embedding toys in soap, and putting pictures of germs on surfaces.