BACKGROUND AND AIM: Inadequate water, sanitation, and hygiene (WaSH) threatens the health of millions of children globally. Urban poor children suffer from health disparities because of inadequate WaSH facilities and limited availability of health education programs in schools. Our study aimed to evaluate the impacts of a school-based WaSH intervention on children’s nutrition status and hydration in Manila, Philippines. METHODS: We conducted a cluster-randomized controlled trial in 15 public schools, assigning two schools to the control group (CG) and randomizing 13 schools to one of three intervention groups (IGs), IGA, IGB, and IGC, which received low-, medium-, and high-intensity health education, respectively. The intervention consisted of: 1) WaSH policy workshops; 2) health education; 3) hygiene supplies; 4) WaSH facilities repairs. We measured: nutrition status (stunting, severe thinness, thinness, overweight, obesity) via anthropometry and the World Health Organization's standards; dehydration, defined as a urine specific gravity (USG) of 1.020 or greater, via urine test strips. RESULTS:Our sample was 756 and 701 children at baseline and end-line (8 months later), respectively (retention rate ~93%). At baseline 11% of children were stunted and 32% did not have a