To assess the nutritional composition, adequacy, and environmental impact of menus served, consumed and wasted by 11–12-year-old students in public and charter schools in northern Spain.

A cross-sectional observational study (2017–2018) involving photographing menus before and after consumption, visual portion size estimation using a validated photographic catalogue, and food waste assessment via the quarter-waste visual method. Nutritional composition was analysed using food composition databases, and greenhouse gas emissions using life cycle assessment data.

Ten primary schools (five public and five charter) in northern Spain.

1,000 school menus for students aged 11–12 years.

Menus served exceeded energy recommendations (791.5±176.7kcal), were high in fat (39.7±13.4g), protein (29.7±10.0g) and sodium (980.4±302.2mg) but low in carbohydrates (74.7±18.1g), fibre (8.8±3.7g) and several micronutrients. Food waste averaged 140.5g per menu, mainly vegetables and fruit, leading to nutrient losses, particularly in fibre, vitamins A and C, and iron. The carbon footprint of menus averaged 1.489 kg CO₂-eq, primarily from meat and fish, with waste contributing 0.298kg CO₂-eq. Public schools served more nutrient-dense food but had higher waste (public 151.5±112.3g vs. charter 129.5±86.3g, p<0.001); charter schools served more energy-dense food, with higher sodium and fat (p<0.001).

Menus showed nutritional imbalances, with excessive energy and sodium and insufficient fibre and several micronutrients. Food waste worsened dietary adequacy while increasing environmental impact. Public schools offered more nutrient-rich food but faced greater waste compared to charter schools. Institutional differences suggest the need for tailored strategies to enhance both nutritional quality and sustainability.