Objective To assess effectiveness of school-based smoking prevention curricula keeping children never-smokers.

Design Systematic review, meta-analysis. Data: MEDLINE (1966+), EMBASE (1974+), Cinahl, PsycINFO (1967+), ERIC (1982+), Cochrane CENTRAL, Health Star, Dissertation Abstracts, conference proceedings. Data synthesis: pooled analyses, fixed-effects models, adjusted ORs. Risk of bias assessed with Cochrane Risk of Bias tool.

Setting 50 randomised controlled trials (RCTs) of school-based smoking curricula.

Participants Never-smokers age 5–18 (n=143 495); follow-up ≥6 months; all countries; no date/language limitations.

Interventions Information, social influences, social competence, combined social influences/competence and multimodal curricula.

Outcome measure Remaining a never-smoker at follow-up.

Results Pooling all curricula, trials with follow-up ≤1 year showed no statistically significant differences compared with controls (OR 0.91 (0.82 to 1.01)), though trials of combined social competence/social influences curricula had a significant effect on smoking prevention (7 trials, OR 0.59 (95% CI 0.41 to 0.85)). Pooling all trials with longest follow-up showed an overall significant effect in favour of the interventions (OR 0.88 (0.82 to 0.95)), as did the social competence (OR 0.65 (0.43 to 0.96)) and combined social competence/social influences curricula (OR 0.60 (0.43 to 0.83)). No effect for information, social influences or multimodal curricula. Principal findings were not sensitive to inclusion of booster sessions in curricula or to whether they were peer-led or adult-led. Differentiation into tobacco-only or multifocal curricula had a similar effect on the primary findings. Few trials assessed outcomes by gender: there were significant effects for females at both follow-up periods, but not for males.

Conclusions RCTs of baseline never-smokers at longest follow-up found an overall significant effect with average 12% reduction in starting smoking compared with controls, but no effect for all trials pooled at ≤1 year. However, combined social competence/social influences curricula showed a significant effect at both follow-up periods.

Systematic review registration Cochrane Tobacco Review Group CD001293.