Weichold 2012 (Teacher).

Methods	Country: Germany Site: 5 Classes in a one Gymnasium in town of 24,000 in Thűringen, E. Germany (3 classes teacher‐led intervention, 1 class peer‐led intervention, 1 class control) Focus: alcohol and tobacco prevention 'Life Skills Program' Design: cluster RCT (Group 2: changes rates)
Participants	Baseline: 105 Age: 10.74 years (mean) Gender: 44% F Ethnicity: German, others not stated Baseline smoking data: prevalence smoking (ever use) teacher‐led intervention group 0.29 mean (0.45 SD), peer‐led intervention group 0.45 mean (0.61 SD), control group 0.35 mean (0.57 SD)
Interventions	Category: social competence and social influences vs. control Programme deliverer: teachers; 4 peers delivered programme to one 5th grade classroom Intervention: (Grade 5: ten 90‐minute and five 45‐minute sessions (in one week); Grade 6 & 7 booster: project day (total three 90‐minute and four 45‐minute project sessions) IPSY (Information + Psychosocial Competence = Protection): generic, intra‐ and interpersonal Life Skills (e.g. communication skills, coping with anxiety and stress, problem solving) with the training of skills related to substance use (e.g. refusal skills). Knowledge concerning alcohol and cigarette use (e.g. actual prevalence rates, short‐term consequences of substance use, advertising strategies), information on the adequate structuring of leisure time, sessions on school issues (e.g. attitudes towards school); interactive teaching methods (role‐play, group discussions). Teacher‐led Peer‐led Control: produced a student newspaper (same time commitment).
Outcomes	Self reports of 1. ever used cigarettes, 2. frequency of smoking previous month (0 = never to 4 = daily) Follow‐up: 2 years
Notes	Quality of intervention delivery: teachers reported they taught the full content of the programme manual in > 90% of the sessions, peer facilitators reported whole content according to IPSY manual for 80% of those sessions. Statistical quality: Was a power computation performed? No Was an intention‐to‐treat analysis performed? No; but 125 at baseline, 122 at 2 year follow‐up. Was a correction for clustering made? No Were appropriate statistical methods used? 2‐way ANOVAS with group and time
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	No method of randomisation stated other than 'classroom‐wise randomisation' Clusters: classes Cluster constraint: not stated Baseline comparability: equivalent on gender, SES, smoking and drinking behaviour of family and friends, adolescent smoking and drinking and resistance skills. "Students in the control group were more likely to come from the town compared to the students of the other two conditions."
Allocation concealment (selection bias)	Unclear risk	No statement
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	No statement
Incomplete outcome data (attrition bias) All outcomes	Low risk	125 at baseline, 122 at 2 year follow‐up
Selective reporting (reporting bias)	Low risk	No selective reporting