Background. Soil-transmitted helminth (STH) infections remain endemic among Nigerian schoolchildren despite mass deworming, and school-based health education is widely promoted to prevent reinfection, improve hygiene, and keep children in class. Nigerian evidence has not previously been synthesised. Objective. To synthesise the effect of school-based health education on hygiene practices, STH infection, and school attendance among Nigerian primary school pupils. Methods. Following PRISMA 2020, we screened 56 records from a curated evidence library (51 after removing five duplicates), applied pre-specified criteria, extracted outcome data, appraised risk of bias, and, where outcomes allowed, pooled school-level proportions with DerSimonian–Laird random-effects models. Two Nigerian studies met the criteria: a pair-matched cluster-randomised trial in Kogi State (10 schools; deworming plus health education versus deworming alone) and a controlled quasi-experimental study in Osun State (404 pupils; 12 schools). Results. In Kogi East, 12-month STH incidence was 7.2% (12/167) with health education and 6.4% (10/157) with deworming alone (odds ratio 1.09, 95% CI 0.45–2.62; I² = 0% within arms); incidence in both arms was about 80% below baseline prevalence (36.1% and 32.0%). In Osun State, the proportion of pupils with good schistosomiasis knowledge rose from 27.9% to 95.0%, and the prevalence of Schistosoma haematobium fell from 16.9% to 3.5% in the intervention group, whereas it stayed near 15.8% in the comparison group; risky practices did not change significantly (88.1% to 83.1%). Neither study measured school attendance. Overall certainty of evidence was very low. Conclusions. Current Nigerian evidence shows that school-based health education reliably improves knowledge and attitudes but has not been shown to reduce STH reinfection beyond deworming alone, and its effect on hygiene practice and attendance is unproven. Adequately powered, cluster-randomised trials that measure observed hygiene behaviour and school attendance, alongside improved school and community sanitation, are needed.