It is interesting to see what French kids have on the menu at their schools. Here is a link that will show you the weekly menu in a random school somewhere in France. You can click on translate to see the page in English. The translation is reasonably good.

https://www.courrierdelouest.fr/actualite/saint-macaire-en-mauges-menus-du-restaurant-scolaire-municipal-jean-moulin-09-03-2019-391124

As you can see, every day’s menu is, it at least a three-course menu. It shows variety and it is rather well-balanced. As a side note, it is also interesting to know that meals are free, as schools are in France, as they are the school of the French Republic. No lunch money needed.