There is an obesity crisis, It is not so called, It is real. Your kids eating chips are starting on a lifetime of foods that will raise their insulin resistance and set them for things like high blood pressure. and diabetes. Let's talk of kids on the transplant list for NAFLD, non alcoholic Fatty Liver Disease, that became NASH and they need a new liver to survive.
The school asking you NOT to send chips is trying to educate you, and your children. The high carb, low fat diet that started in the 1980s set us into a global crisis where there are more people who are overweight and obese globally, than starving.
Incidentally, this lovely constant attack on the liver, is also likely related to the fantastic growth in dementia. Yes, it is diet related. They are not moralizing, and I am not moralizing either. You can eat a bad diet, and it sounds like you have no problem with it, but you can't escape it.
Facts are like pesky and shit.