Background: Soil-transmitted helminths (STH) cause substantial disease and disability globally. Health education has proven complementary to school-based drug administration programs for STH control. We determined the generalizability of the impact of “The Magic Glasses” health education package for STH prevention in schoolchildren in Laguna province, the Philippines, having previously shown its positive impact in China. Methods: We conducted a cluster-randomised controlled trial, in schoolchildren, aged 9–10 years, across 40 schools over one year. Schools were randomly assigned either to the “Magic Glasses Philippines” health education intervention package (consisting of a cartoon video, classroom discussions, drawing and essay competition) complementing the standard health education activities of the Philippines Departments of Health and Education, or to a control group, which involved only the standard health education activities. The primary trial outcomes were the proportion of STH infected schoolchildren and their knowledge, attitude and behaviour of STH assessed in both groups at baseline and through two follow-up surveys undertaken immediately prior to the semi-annual national mass administration of albendazole. The outcomes between the study arms were compared using generalized estimating equation models, accounting for clustering at the school level. The trial is registered with Australian New Zealand Clinical Trials Registry number: ACTRN12616000508471 Findings: At follow-up assessments, the mean knowledge and behaviour scores in the intervention group were, respectively, 5·3 (95% confidence interval [CI]:4·2[sbnd]6·5; p=<0.001) and 1·1 (95% CI: 0·4[sbnd]1·7; p=0.002) percentage points higher than the control group. There was no overall effect on helminth infections (any STH; adjusted odds ratio [aOR]:1·0; 95% CI: 0·8[sbnd]1·3; p=0·856), Ascaris lumbricoides; aOR:1·0; 95% CI: 0·7[sbnd]1·6; p=0·894, or Trichuris trichiura; aOR:1·7; 95% CI: 0·9[sbnd]1·6; p=0·315) but sub-group analysis showed a 60% reduction in the odds of any STH infection resulting from the “Magic Glasses” intervention in schools with a baseline prevalence ≤15% (aOR: 0·4; 95% CI: 0·2[sbnd]0·7; p=0·001). Interpretation: The health-education package demonstrated a modest but statistically significant impact on the students’ overall STH knowledge and changes in their behaviour but was only effective in preventing STH infections in intervention schools where the baseline prevalence was ≤15%. Funding: National Health and Medical Research Council, Australia, and the UBS-Optimus Foundation, Switzerland.