O'Donnell 1995.

Methods	Country: USA Site: Seattle 'Seattle Social Development Project' Focus: School failure, drug abuse, delinquency Design: RCT (excluded from analysis)
Participants	Baseline: 424 Age: 5th grade (10 ‐ 11 years) Gender: 48% F Ethnicity: 49% European American, 22% African American, 19% Asian‐American, 6% Native American, 4% Other Baseline smoking data: not stated
Interventions	Category: social competence vs. control Programme deliverer: teachers Intervention: Classroom intervention: teachers trained in proactive classroom management, interactive teaching, and co‐operative learning Child intervention: cognitive and social skills training to solve problems (communication, decision making, negotiation, conflict resolution skills); recognition of trouble, identify legal name of trouble, name consequences, generate positive alternatives to stay out of trouble Parent intervention: parent training classes on child behaviour management, academic support, antisocial prevention and goals Control: teachers did not receive training in instructional skills; teachers were observed to document their teaching practices during four classes on different days
Outcomes	Smoked cigarettes (not further defined) Follow‐up: 1.5 years from baseline
Notes	Quality of intervention delivery: Teachers observed and given feedback every 3 weeks; control teachers observed over 4 periods to document their teaching practices; no numerical presentation of process analysis Statistical quality: Was a power computation performed? No Was an intention‐to‐treat analysis performed? Not stated Was a correction for clustering made? No Were appropriate statistical methods used? Non‐randomly assigned groups not separated from randomly assigned; students randomly assigned as individuals or to classes not separately analysed; statistical method not stated; apparently by differences of means; students in intervention or control groups enrolled in 5th or 6th grade for < 1 semester were excluded from the analysis.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	In 1981, 2 schools assigned to either intervention or control and then students in the remaining 6 schools randomly assigned; then from 1981 ‐ 1984 newly entering students were randomly assigned to intervention or control classrooms; and in 1985 study expanded to include all 18 Seattle elementary schools. Method of randomisation not stated Clusters: not clear, schools, individuals and subsequently classes Cluster constraint: not stated Baseline comparability: not stated
Allocation concealment (selection bias)	High risk	Inadequate
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	No statement
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	40% attrition; no differential attrition Baseline 1985 when entered 5th grade: results are reported only for 177 low income students (42%) from the 424 students in 5th grade; Completion of 6th grade in 1987: 106 (60%) of the low income group completed 6th grade surveys.
Selective reporting (reporting bias)	Unclear risk	No statement