Wow haha, I thought my use of amurikuh and frogs were a dead giveaway that I wasn't being serious, but I guess I under estimated the serious squad. If you really want to debate this ridiculousness then ok:
It's not an issue of health they're attacking, it's the degradation of their culture in kids eating habits. If people want to preserve culture fine, but don't legislate it and force it down people's throats. Instead offer more options, programs to involve parents who wish in activities to help promote culture in the home, but taking away their choices to force them to enjoy french food won't do shit. All it'll do is make the kids resent the food and the lack of what they enjoyed before, not magically make them love food that they were masking with condiments before.
It's blatant xenophobia, and honestly is ridiculous as hell. Something like culture and food should be preserved via families, not mandates. People should be able to make choices, and kids are still people. They shouldn't be allowed free reign over everything no, but something like what they want for lunch out of what is offered via the school isn't a big deal. If this is a health issue then fine, frame it in that light and overhaul your school menu, I doubt all the french foods are magically bastions of health.
If you want to preserve culture, offer more options, develop programs for parents that wish to get involved with and involve their kids in (parents pass down recipes, not bureaucrats). If you want to overhaul the nutrition of the meals, make that the issue, make that the claim and look at everything, not just one aspect unrelated. Not all French condiments are healthy, desert is most likely unhealthy; if they're trying to do that they're doing a shit job, and if they're being xenophobic they're doing a great job at that too.