School Meals in Denmark: Evaluation of a National School Meal Pilot Program on Children's Health, Learning and Well-being - a Natural Experiment

School Meals in Denmark is a prospective, open-label, matched-pair cluster-randomized controlled study conducted as a natural experiment alongside the Danish National School Meal Pilot Program. As allocation to the national program is determined by the Danish Ministry of Children and Education and not by the investigators, the study evaluates the effects of school meals under real-world conditions without introducing an additional experimental intervention.

Approximately 3,200 children in grades 3, 4, and 7 from 32 public schools are included. Participating schools are matched in pairs based on socioeconomic and geographic characteristics using national statistical data. Recruitment includes schools implementing the program either at the middle grades or at the lower secondary level. At each school, intervention classes are identified at the grade level receiving school meals.

Control classes are recruited pragmatically from the same schools but at a different grade level than the intervention classes. Intervention effects are estimated by comparing classes at the same grade level across matched schools, where one school implements the school meal program at that grade and the matched school does not. This approach allows for within-school control recruitment while preserving between-school comparisons at the same grade level.

Data are collected at two time points over a follow-up period of approximately 1.5 years using a pre-post design. Outcomes include anthropometric measures (height, weight, body composition assessed by bioelectrical impedance), cardiovascular indicators (blood pressure and resting heart rate), tablet-based cognitive performance tests, and child-reported questionnaires on well-being and psychosocial functioning. Parents complete brief electronic questionnaires addressing their child's psychosocial functioning and dietary habits.

In addition, observations of school meal settings are conducted to assess food intake and food waste, and menu plans from meal providers are collected to evaluate nutritional quality and compliance with dietary guidelines.