Project EX‐1 2001.

Methods	Country: USA Setting: 18 continuation high schools in Southern California Study design: cluster‐RCT (assigned by block randomization)
Participants	Participants: 335 smokers, recruited by advertising and flyers within each school. 139 in 6 Project EX schools, 120 in 6 Project EX plus 'school as community' (SAC) schools, 76 in 6 control schools. Age range: 14‐19 years. Mean age was 16.8 (± 0.8) years Criterion for inclusion: used tobacco in last 30 days Follow‐up method: questionnaires and telephone for those who had left school Inducements to enter study: class credits and class release time Pre‐study smoking status assessment: questionnaire. Mean smoking 8.8 cpd ( ± 9.3) mFTQ scores 30% in range 0‐6, 53% in range 7‐13 and 17% in range 14‐21 Post‐study smoking status assessment: questionnaires No significant demographic differences between arms of trial
Interventions	Intervention: initially schools split into 3 arms: (1) Project EX sessions alone (clinic‐only schools). (2) Project EX plus school community development 'school‐as‐community' (SAC schools). (3) Control: standard care 1. Project Ex was 8 sessions or 'clinics' over a 6‐week period delivered to groups and developed in trials. 4 sessions were preparation for quitting over 2 weeks, and next 4 were weekly during the first month post‐quit Theoretical basis of intervention: complex theoretical constructs including MI etc, and including games for groups, education and anger management, yoga, weight control, meditation, assertiveness training, role play and relapse prevention 2. SAC intervention: modelled on Toward No Drug Abuse programme. Student body organized service, recreational and job training functions, and produced a Project newsletter, to enable expression of anti‐tobacco attitudes.
Outcomes	Measurement: 30‐day PPA; Follow‐up periods: > 3 months, 6 months from start of study Verification: CO (for 62 students and results adjusted by false quit reporting factor of this group) Losses to follow‐up: 51% in intervention group ‐ 40% of intervention group dropped out during clinics ‐ 42% in control group lost to follow‐up. Results: no difference in outcomes between two intervention arms of trial so study authors pooled data and compared, as a single arm with control arm Calculated OR based on 17% in intervention = 44 people and 8% in control being 6 people Calculated OR = 2.388 (0.976 to 5.841)
Notes	Recruitment in intervention arm was voluntary; 90% of participants said they had volunteered because they wanted help with quitting
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"Randomized block design procedure," method not specified
Allocation concealment (selection bias)	Low risk	Students recruited after schools randomized
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Not specified
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Biochemical validation used for 62 students and results adjusted by false quit reporting factor of this group
Incomplete outcome data (attrition bias) All outcomes	Low risk	Per‐protocol analysis and ITT analysis yield similar outcomes, "evidence that the study findings are robust despite the relatively high clinic drop‐out rate."