Not that easy - there's lunchroom 'cops' 'trained' to make sure bagged lunches are nutritionally sound - if not - they get confiscated and go to the lunch line.
Wow! Things have changed! Big brother is here! I have no kids in school, but it would be a cold day in he## they would do that to my kids. I would sue their pants off.
My kids went to Catholic school where the parents were responsible.