There are many differences between the French school system and the British one. Here is one.
In Cardiff, we were always told when the children were going to do something with food, and eat something. We were asked to let the school know if we didn’t want our child to eat this type of food. No such thing in France. Jean-Baptiste has had different cakes, they’ve even baked at school. But we’ve never been asked before hand whether he was allowed to. I suppose it would be our responsibility to let them know at the beginning of the year that he had any food allergies. But also, the school system being thoroughly secular, they wouldn’t asked if you have any special diet on the ground of religion, since religion is completely excluded from the school system.