1) Supermarket processed food already has these labels.
2) If I have a problem with my school's food I take it to my school.
The individual school can't do anything about it. (unless it's a private school, but most private schools use the same suppliers)
The school boards make those decisions and they will go with the lowest bidder.
If by some miracle the entire citizenry stood up and said "change it". The school board would acquiesce, but inform the citizens that higher property tax would be need to pay for the better quality food and the "concerned citizens" would suddenly vanish.

