I was sick a few months ago and DH was in charge of lunches and snacks. For some odd reason, he decided to pack Hershey bars for snack - not exactly healthy (in DH's defense, he peddles chocolate to DS1 as a food high in fat because of his weight issues).
Snack time rolls around and both boys had their chocolate bars taken away and replaced with raisins (that I had provided previously on the off chance they forgot their snacks). Both teachers assumed that the boys either packed their own snack and I got notes home explaining the issue. Fine, they replaced food with food that I had previously approved.
I don't have a problem with a note coming home explaining what they think is missing from my child's lunch to give me a chance to have an open discussion with them. DS1 doesn't eat "grains" at school per se because his bread is rather sensitive to temperatures because of molding and textures. He eats bread at home. I know there are other options out there for him but obviously limited by allergies. But I would like the oppurtunity to discuss that without the school lunch being forced on him.
The irony - we can force a "healthy" lunch on your child but will do nothing to stop the cupcakes, candy and other extraneous foods being shoved in their face.