Table 1. Study eligibility and exclusion criteria.

Inclusion criteria
Design	Randomised and non-randomised controlled trials that allocated students individually or in clusters (i.e. teachers, classrooms, schools), and that used pre-test/post-test, post-test only, and interrupted time series designs
Setting	Middle schools, secondary schools, high schools or other equivalent educational institutions
Participants	Children and adolescents aged 11 to 18
Intervention	All types of educational interventions meant to facilitate abilities in critical appraisal of health claimsa by advancing knowledge about science in one or more of the following learning areas as defined by Ryder [17]: •    Study design issues (e.g. experimental studies, blinding, placebos, control groups, observational studies) •    Assessing the certainty of data (e.g. variability and uncertainty of measurement, estimates of measurement variability) •    Interpretation of data (e.g. distinction of correlation and causation, sample size and sampling errors) •    Uncertainty in science (e.g. complexity of variables, restrictions on study designs, estimates of risks) •    Science communication (e.g. the role of peer review, conflicts of interest, deficiencies in media reports of research findings)
Comparison	All comparisons: different educational intervention; different methods of delivery, educational contents, intervention dosages, or the like; regular classes (‘usual care’); no intervention
Outcomes	Primary: Critical appraisal abilities within at least one of the following domains [34]: •    Knowledge and understanding: retention of facts and concepts related to critical appraisal (e.g. recognise the need for control groups to justify health claims about causality; understanding that health claims can never be proven, and accordingly health decisions may be based on estimates of risk). •    Skills: ability to apply knowledge (e.g. ability to judge the credibility of a media report about a health risk). •    Behaviour: transferring the knowledge and skills specified above to everyday situations (e.g. when scanning Web pages for information on a health problem or lifestyle issue). Secondary: •    Attitudes, values, and beliefs related to the importance and usefulness of critical appraisal to inform decisions about health. •    Participation in or completion of, attendance at, and reactions to the learning experience (e.g. participation in class, time spent on class activities, and satisfaction with the educational intervention). Outcome measurements: self-report and direct measures; validated and non-validated measurement instruments.
Exclusion criteria	Studies •    of adolescents who were in the target age range, but attending post-secondary education. •    that evaluated interventions aimed at teachers, but did not measure relevant student outcomes. •    for which the educational intervention was part of a complex intervention or larger study, and it was not possible to extract results from that specific intervention separately. •    of regular health education interventions (e.g. teaching about the benefits of healthy eating or the dangers of smoking) •    of intervention to facilitate scientific content knowledge (e.g. basic principles of gene inheritance or human organ system functioning) •    of health-related media literacy interventions involving critical examination of claims without addressing the learning areas related to knowledge about science as defined above

^aClaims about conventional medical treatments, complementary and alternative treatments, risks/harms, health conditions, diseases, and physical or mental well-being