Implementation of the Norwegian school meal guideline: Development and reliability of two questionnaires to measure adherence

Aims: This article reports on the development and reliability of two questionnaires that measure adherence to the Norwegian National Guideline on Food and Meals in School among primary schools and after-school services. Methods: Questionnaires for school principals and after-school leaders were developed systematically, using the following steps: (a) selection of scope, questions and adherence values; (b) face validity testing through expert review of initial drafts; (c) content validity testing through 19 cognitive interviews; (d) assessment of test–retest reliability in samples of principals (n = 54) and after-school leaders (n = 47); and (e) development of adherence indices. Results: The cognitive interviews led to substantial revisions of the draft questionnaires, increasing content validity through improved relevance and clarity. Test–retest assessment showed that Cohen’s κ ranged from −0.03 to 1.0 for principals and from −0.05 to 0.98 for after-school leaders, with 64 and 53% of values rated as ‘substantial’ or better. Percentage agreement averaged 85% among principals and 82% among after-school leaders. Intraclass correlation for the adherence index scores was 0.84 for principals and 0.91 for after-school leaders. Guideline adherence had a wide range in our samples, with an average of 71% for schools and 76% for after-school services. Conclusion: The questionnaires for measuring adherence to the national school meal guideline among primary schools and after-school services are sufficiently reliable for future use in public health evaluation and research.