By feeding more than thirty million schoolchildren daily, the National School Lunch Program's food offerings substantially influence a contributing factor to climate change: US food production methods. Modifying school lunch nutrition standards could be a policy strategy to reduce climate change while promoting human health. To estimate how school lunches could be adjusted to encourage both outcomes, we compared the composition of school lunches with the EAT-Lancet Commission's healthy reference diet science-based benchmarks for reducing food system impacts on climate change. Analyzing more than 5,000 lunches served in the US during school year 2014-15, we found that they exceeded EAT-Lancet targets for dairy, fruit, refined grains, red meat, and starchy vegetables while containing insufficient whole grains, legumes, vegetables, and nuts. In addition, estimated food costs were higher for school lunches than for lunches meeting EAT-Lancet targets. Our findings suggest that redesigning school lunches could provide high-quality nutrition while benefiting the environment and reducing food costs.