Can you show how the parent's care for their child was usurped in any way shape or form by a child being offered additional food items?
She was told her lunch wasn't good enough, she had her lunch replaced (not taken away) with a school lunch. That is not "supplementing" that is "usurping".
She still had her original lunch. It wasn't replaced.
What's next, the teacher will take away bargain tennis shoes and bill the parents for NIKEs that don't fit?