Just wanted to add the following -- it is from "Responsibilities of a Substitute" from Loudoun County, Virginia Public Schools:
Food and Rewards. Do not give food of any kind to students. Allergies are prevalent in our school system and some students may have severe and even life-threatening reactions to the most innocent of treats. Rewards such as stickers are encouraged but a note left for the teacher to acknowledge good behavior is usually the best option.
Link: (page 31)
http://www.lcps.org/cms/lib4/VA01000195/Centricity/domain/69/subcentral/Substitute%20Guide%202012-13%20PDF.pdf
No reason why this cannot be the rules for the regular teacher too -- at ANY school!
Just something for thought as you work to fix things with your school.
As part of the county's food allergy policy, it is also recommended that teachers not use food as rewards. However, in my experience we've had at least one teacher not do that and then that teacher had the nerve to ask me if she could give DD a food treat (Lifesavers) in front of DD. Nice way to put me on the spot and make me the bad guy again.