Byrne 2005.

Methods	Country: Australia Sites: Canberra high schools (intervention), high and secondary schools in Canberra and Adelaide (control). Focus: Smoking rates of participants Design: Cluster RCT (Group 1: never smoking prevention cohort, not included in analysis).
Participants	Baseline: 2719 (intervention), 6410 (control). Age: 11 ‐ 17 years (grades 7‐10). Gender: 48% M (intervention), 52% M (control). Ethnicity: Not stated. Baseline smoking data: Rates of smoking over previous 12m at outset. Health programme = 9.7%, fitness programme = 9.5%, social skills = 12.5%, control = 14.4%.
Interventions	Category: Social Influences vs information. Programme deliverer: Usual class teachers (all trained by research group) Intervention: 3 programmes aimed at knowledge acquisition and behaviour change. Each programme based on four class sessions which had a distinctive active learning approach: Health programme (biological effects of smoking, smoking and illnesses, smoking rates in Australia and worldwide, smoking as addiction, effects of smoking prevention/cessation on health). Fitness programme (biological effects of smoking, smoking and fitness, smoking and impaired sports ability, smoking among professional athletes, smoking and sporting image). Social skills and stress management programme (smoking, self esteem, perceived maturity, smoking as social behaviour, smoking and social confidence, media influences on smoking, stress and smoking, smoking and social confidence, life skills and resistance to peer pressure, stress management). Control: Non‐randomised, from a separate, older study. No stated intervention.
Outcomes	Smoking behaviour. Self reported Follow‐up: Immediately after intervention (intervention), end of one yr study (intervention and control).
Notes	Quality of intervention delivery: No comment on quality of delivered material, or how many of the sessions were completed, or how many sessions participants attended. Statistical quality: Was a power computation performed? "the design had sufficient statistical power to provide an adequate test of the effectiveness of interventions" (but no power computations presented). Was an intention‐to‐treat analysis performed? No. Was a correction for clustering made? No. Were appropriate statistical methods used? Χ² appropriate for categorical data. No correction for multiple comparisons. Analysis only on participants who completed all three data collection points in intervention group. Control group only two collections points – intake and 12m. Control group data from previous study and only limited. Can only analyse between interventions, not vs control.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"Schools were selected to reflect socioeconomic diversity across the city". Classes within selected schools randomised to one of three intervention programmes. No method of randomisation stated. No controls within selected schools. Control group from previous study.  Clusters: Schools Cluster constraint: Not stated. Baseline comparability: No significant differences in smoking rates at baseline between groups. Classes did not differ on gender and had representations in classes from all age groups in the school (intervention).
Allocation concealment (selection bias)	Unclear risk	Not stated
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	As classes were within the same school there was no mention of how the study dealt with interclass discussion and comparison of interventions.
Incomplete outcome data (attrition bias) All outcomes	High risk	Intervention group: 86.2% of the original group had completed data immediately after intervention (n = 2344).  At end of one yr 62.3% completed follow up (n = 1694). No differential attrition analysis. Control group: 65.5% of the original cohort completed the 12m follow‐up (n = 4198). No explanation of low levels of response at 12m.
Selective reporting (reporting bias)	Low risk	Only goal was reporting smoking outcomes.