What school would this be exactly? If it’s the primary school you’re currently sending your child to, and you disagree with their snack policy, do you have the right to present a challenge to the school board? Do other parents agree with your assessment and are willing to back you?

I have a theory that this school’s policy stems from a desire to limit the kids’ sugar intake during school hours, which makes it easier to manage behavior. If that’s the case, what “science” says about kid’s nutrition will only go so far. They’ll have their own research to rebut your complaint, and while I’m not trying to discourage you, you might find it to be an uphill battle to get them to modify their policy.