Storr 2002 (CC).

Methods	Country: USA Site: 9 public primary schools in Baltimore Focus: classroom management Design: cluster RCT (Group 1: never smoking prevention cohort)
Participants	Baseline: 678 Age: 5.3 ‐ 7.7 years (av 5.7) Gender: 47% F Ethnicity: 86% African Americans, 14% European heritage Baseline smoking data: As age 6, assumed no smoking
Interventions	Category: social competence vs. social competence vs. control (classroom management vs. teachers communicating with parents vs. usual contact control) Programme deliverer: teachers Intervention: The Classroom‐Centered (CC) Intervention: (a) language and maths curricula were enhanced with materials to encourage skills in critical thinking, composition, listening and comprehension; (b) whole‐class strategies to encourage problem solving by children in group contexts, decrease aggressive behaviour, and encourage time on task; (c) strategies for children not performing adequately. Teams of children received points for good behaviour and lost points for behaviours such as starting fights. Points could be exchanged for classroom activities, game periods and stickers. The Family‐School Partnership (FSP): (a) the 'Parents on Your Side Program' trained teachers to communicate with parents and build partnerships, with a 3‐day workshop, a training manual; and follow‐up supervisory visits; (b) weekly home‐school learning and communicating activities; (c) 9 workshops for parents. Control: usual curriculum and parent‐teacher communications
Outcomes	Self reported time to initiation of smoking Follow‐up: At age 12, "... 6 years after end of intervention year..."
Notes	Quality of intervention delivery: implementation scores for the CC intervention averaged 60% (range 30% to 78%), and parents in the FSP intervention attended an average of 4/7 sessions; teachers received 60 hrs of training and attended monthly meetings to discuss intervention issues and receive support; fidelity to the interventions was assessed at the monthly meetings and during observation of 3 classroom sessions during the year; the FSP group teachers were asked to document all contacts with parents; and parents reported on the interventions and the skill of the presenters; teachers rated the child's adaptation to school on a 6‐point scale and family and household characteristics were assessed in a 60‐min interview with parents. Statistical quality: Was a power computation performed? The power computation assessed that 150 children per group would be needed; with an av 30% cumulative risk of initiating smoking; between‐group relative risk of initiating smoking = 1.75; and alpha 0.05, 2‐tailed for 80% power. Was an intention‐to‐treat analysis performed? Yes Was a correction for clustering made? No Were appropriate statistical methods used? Yes. Analysis was by general estimating equations with a multivariate response profile approach; Cox regression models to estimate risk of starting smoking.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"Within each school, children and teachers were randomly assigned to one of two intervention or control classrooms."; (an e‐mail from Dr. Ialongo states that an SAS programme generated the class lists and randomly assigned students; that children and teachers were randomly assigned to 1st grade within each of the 9 participating schools; and that there was balancing for gender and kindergarten teacher ratings of aggressive disruptive behaviour and academic readiness). Clusters: classrooms Cluster constraints: "A randomised block design was employed, with each of the nine schools serving as a blocking factor..." Baseline comparability: Children in control group somewhat less likely to be male, and African American, more likely to be from 2 parent households, teacher ratings of problem behaviour higher in CC group; these differences were statistically adjusted in the analyses.
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	Storr 2002 (Figure 1): Of the 678 pupils who entered Grade 1, 549 at 6 year (7th grade) follow‐up (189 CC, 192 FS, 168 control); Furr‐Holden 2004 reported ‐ "At follow‐up, 5, 6, 7 years after randomisation (sixth through eighth grades), approximately 84% (566/678) of the sample was available.". No differential attrition among groups across baseline characteristics or smoking status.
Selective reporting (reporting bias)	Low risk	No selective reporting