OBJECTIVE : This work analyses the meal supply in primary schools in Italy to highlight new areas of inefficiency upstream of the food chain, regarding the size of the food portions specified in public tenders. A lack of conformity of food portions can potentially lead to a double negative externality affecting the sustainability of school meals: overweight children and food waste. METHODS : Based on the data contained in the contract between municipalities and school catering services, the analysis was performed on the portion sizes (in grams) of the main food products included in the school menu for each regional capital (RC) in Italy. Data analysis regarded two main aspects: consistency of food portions within regions and adherence to national standards for childrens. RESULTS : The results revealed great discrepancies amongst regions and in several cases, portion sizes significantly larger than the reference values of standard portions for school catering. The study also profiles RC on the basis of portion sizes, school meal attendance, and childhood obesity rates. CONCLUSIONS : School meals have the potential to educate the next generation regarding healthy eating habits, and thus play a leading role in obesity prevention in children. Similarly, the educational role of eating at school can contribute to raising children's awareness about one of the most urgent environmental challenges-food waste-by introducing the best strategies for waste reduction, reuse, and recycling. Results have economic, social, health, and environmental implications and highlight the need to revisit policies to introduce new solutions for more sustainable and healthy school canteens in Italy. METHODS : Level V, descriptive studies.