Hecht 2008.

Methods	Country: USA Site: 23 middle schools in Phoenix, Arizona (13 intervention, 10 control). "Students in six additional schools participated in a third condition of the study, in which they received a new version of the kiR which focused on acculturation issues". Focus: Prevention and reduction of alcohol, drugs, marijuana and tobacco. Design: Cluster RCT (excluded from analysis).
Participants	Baseline: Baseline = Wave 1: Hecht 2008: 1566 students (768 intervention, 798 control); Elek 2010: 1984. Age: 10.4 average (range 7 ‐ 15) at Wave 1, baseline. Gender: 49.1% F (Table), 49.7% F (text). Ethnicity: 75% Latin American, Mexican or Other Latino, 4.9% W, 9.1% B, 2.6% N‐A, 0.4% Asian American, 7.8% not stated. Baseline smoking data: Not stated.
Interventions	Category: Social influences and social competence vs social influences [Project ALERT or local programmes]. Programme deliverer: Regular classroom teachers (training prior to teaching curriculum). Intervention: kiR‐Plus Adapted from 7th grade Keep it REAL (kiR) for 5th graders: 12 lessons, Drug Resistance Skills kiR curriculum; 4 resistance skills with videos followed by guided discussion  (Refuse, Explain, Avoid, Leave [ REAL]). Elek 2010 notes that half of the classes in each grade level received kiR‐Plus and half received kiR‐Acculturation Enhanced (AE) . Control: Students in 7 control schools participated in Project ALERT in 5th or 6th grade; some control schools used Gonzo’s 20 Ground Rules (Communities in Schools in Arizona, 2007); some used Red Ribbon Week (National Family Partnership, 2005).
Outcomes	Lifetime prevalence/tried ('even if it was only once or only a little'); Cigarettes past 30 days (0 = 0, 1 = any) Follow‐up: Post‐intervention, post‐booster sessions.
Notes	Quality of intervention delivery: "Lesson observation by the study personnel indicated that the teachers in the multicultural condition implemented the kiR intervention with both high quality (organization, preparation, student participation, student enjoyment, etc.) and fidelity (of instruction, video presentation, student practice, and homework). Teachers implementing the kiR intervention self‐reported presentation of all program lessons and activities". Statistical quality: Was a power computation performed? No. Was an intention‐to‐treat analysis performed? Not, but authors state used multiple imputation NORM software for missing data. Was a correction for clustering made? Yes, Stata complex survey sample routines to account for ICCs in classes. Were appropriate statistical methods used? Stata survey programme for %s, means and SEs and complex survey sample routines to account for ICCs in classes; multiple imputation NORM software control for imputed data; linear mixed effects regression.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"10 schools were randomly assigned to the intervention conditions, 13 schools to the control condition". No method of randomisation. Clusters: Schools Cluster constraint: Not stated. Baseline comparability: No differences on lifetime substance use at baseline, no use in past month, or characteristics correlated with substance use.
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	Unclear risk	Baseline to wave 3 = 28% Missing data: NORM software used to produce 10 multiply‐imputed datasets for missing data.
Selective reporting (reporting bias)	Low risk	No selective reporting