Coyle 2006.

Methods	Design: cluster randomized trial; 24 schools assigned to intervention or control Location: northern California, USA Time frame: recruited 2000 to 2001 Sample size calculation (and outcome of focus): no information
Participants	General with N: 24 alternative day schools; 988 students (ages 14 to > 18 years) Inclusion criteria: 4 counties with ethnic diversity and in close proximity to investigators; all enrolled students (generally had severe discipline issues, substance use, or chronic absenteeism) Exclusion criteria: students on extended leave (e.g. maternity or medical); suspended or incarcerated at baseline; functionally dropped out of school
Interventions	Study focus: Prevention of HIV, STI, and pregnancy Theory or model: Social Cognitive Theory + Theory of Planned Behavior (+ earlier Theory of Reasoned Action) Intervention: based on that in Coyle 2001; skills‐based HIV, STD, and pregnancy‐prevention curriculum (9 sessions; 13.5 hours total) + service‐learning activities (5 visits to volunteer sites; 12.5 hours total); implemented 2 or 3 times per week for 5 to 7 weeks Comparison: usual activities related to prevention of HIV, STI, and pregnancy (typically presenters from community‐based agencies)
Outcomes	Primary: frequency of sex without condom in past 3 months, condom use with last sex, use of effective birth control, pregnancy (self‐report) Secondary: attitude toward condoms (general, protecting against STDs or pregnancy); knowledge of condoms or HIV and condoms; self efficacy Follow‐up: 6, 12, and 18 months after baseline (about 5, 11, and 17 months postprogram)
Notes	Report provided effect estimates but not means or frequencies per study group; unable to obtain further information from investigator.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Restricted randomization: schools put into matched sets, matched groups formed with set from each county, and matched groups randomized
Allocation concealment (selection bias)	Unclear risk	Schools identified prior to randomization. All students in schools were eligible.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Presume no blinding of participants or providers; not feasible due to type of intervention
Blinding of outcome assessment (detection bias)	Unclear risk	No mention
Outcome measures	High risk	Self‐report of contraceptive use and pregnancy
Incomplete outcome data (attrition bias) All outcomes	High risk	Loss to follow‐up: after baseline 6 months, 27% (immediately postprogram); 12 months, 38% (6 months postprogram); 18 months, 44% (12 months postprogram) Loss by group not reported
Other bias	High risk	Analysis for cluster randomized trial: multilevel models (levels student and school); psychosocial outcomes also had survey measurement occasion Predictor variables in models: baseline responses on outcome, intervention group, and “outcome specific covariates” (related to outcome and intervention; unspecified) Analysis of behavioral outcomes based on who had sex (could be affected by intervention), rather than all randomized (high risk)