Atherly 2009.

Methods	Included as outcome evaluation Study design: clustered parallel‐group RCT Setting: junior high and high schools Period: 2003‐2004 school year
Participants	Eligible sample frame: not reported Randomised: numbers for these data are disaggregated. The study included 524 children: 458 children randomised at the school level: 225 to the intervention group; and 233 to the control group Completed (intervention): 458 Inclusion criteria: not reported Exclusion criteria: not reported Baseline characteristics Age of children: mean age, 13.9 in the intervention group; 13.4 in the control group Ethnicity: not reported Socio‐economic status: not reported Gender: 46.6% female in the intervention group; 50.7% female in the control group Asthma status: asthmatic children only
Interventions	Intervention: the Power Breathing programme focused on education about asthma, asthma control strategies, and psychosocial concerns Control: not reported Intensity: three 90‐minute educational sessions Instructor: teachers and school nurses were involved in the intervention; however their role is unclear Theoretical framework: not reported Parental engagement: not reported Child satisfaction: not reported Timing of intervention in school day: not reported
Outcomes	Extractable outcomes were collected for: Exacerbations leading to admission to hospital Asthma symptoms leading to an emergency hospital visit Experience of daytime and night‐time symptoms
Notes	Study presented an economic evaluation of the intervention Considered for inclusion as a process evaluation but not deemed to fulfil the criteria of a process evaluation Funding source: not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	No detail provided on random assignment procedures "The schools were then randomly assigned to the intervention or control group"
Allocation concealment (selection bias)	Unclear risk	Not addressed by study authors
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Not addressed by study authors
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not addressed by study authors
Incomplete outcome data (attrition bias) All outcomes	High risk	Although attrition was relatively low overall, the study did not provide details of the spread of attrition across arms and was deemed at high risk of bias "The study included 524 adolescents in grades 6–12 from middle and high schools. Surveys were administered at baseline, immediately postintervention and three months post‐intervention. A total of 458 children completed all surveys, including 225 in the intervention group and 233 in the control group"
Selective reporting (reporting bias)	Low risk	No evidence of selective reporting
Other bias	High risk	Missingness ‐ low risk ‐ besides attrition, no additional missing data were reported Baseline imbalance ‐ high risk ‐ indications showed poorer asthma control at baseline in the control group (e.g. higher level of ED visits) Risk of contamination ‐ low ‐ randomisation occurred at a school level
Transparent and clearly stated aims	Unclear risk	N/A
Explicit theories underpinning and/or literature review	Unclear risk	N/A
Transparent and clearly stated methods and tools	Unclear risk	N/A
Selective reporting	Unclear risk	N/A
Harmful effects	Unclear risk	N/A
Population and sample described well	Unclear risk	N/A
Continuous evaluation	Unclear risk	N/A
Evaluation participation equity and sampling	Unclear risk	N/A
Design and methods overall approach	Unclear risk	N/A
Tools and methods of data collection reliable/credible	Unclear risk	N/A
Tools and methods of data analysis reliable/credible	Unclear risk	N/A
Performance bias/neutrality/credibility/conformability	Unclear risk	N/A
Reliability of findings and recommendations	Unclear risk	N/A
Transferability of findings	Unclear risk	N/A
Overall risk of bias of process evaluation	Unclear risk	N/A