Objective: To evaluate evidence of the effectiveness of school-based behavioural interventions to improve the oral health of children aged 3-18 years in a rapid review of randomised controlled trials (RCTs). Methods: Three independent reviewers searched MEDLINE, EMBASE, Web of Science and other sources between January 2000 and December 2020 for eligible published and unpublished studies in English and extracted data. Primary outcomes were caries increment, plaque levels, gingival health, reported frequency and/or amount of free sugars intake and oral hygiene behaviour. Risk of bias was assessed using the Cochrane criteria. Results: Eight cluster RCTs met the inclusion criteria and had substantial heterogeneity. Three trials assessed caries increment and one found significant reductions in the intervention group. Another trial found similar benefits, but these were limited to children from high socioeconomic groups. The third trial found an increase in dental caries in the intervention group. Three studies reported significant reductions in plaque scores and improvements in gingival health with modest effects. Interventions delivered by peers (at adolescence) or with parents’ involvement (at pre-adolescence) showed significant reductions in plaque scores compared to those delivered by dentists or teachers only. Most interventions showed significant improvements in self-reported behaviours. Conclusions: There is limited evidence of clinical benefit to dental health from school-based behavioural interventions. There is a need to conduct well-designed trials of behavioural interventions that are theory-derived and include environmental elements (e.g. supervised toothbrushing). Future trials would benefit from cost-effectiveness analysis and assessment of interventions’ effect on oral health inequalities amongst children. Keywords: Review, Adolescent, Health behavior, Oral health, School, Child