Yup, they can do this. They can stonewall and refuse all kinds of accommodations . . . you just have to keep hammering away.
First, welcome and glad you found us!
Second, do you have a strong letter from the child's allergist . . . hopefully with lists of the accommodations you've outlined? (Or is your allergist pretty hands off, as some can be?)
Does your school district have any published "How to manage" food allergy policies that might be helpful as you try to work with the school?
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The FIRST thing I would be doing is, in writing, have them IMMEDIATELY correct the 504 to include all known allergens. I would also attach the copy of signed MEDICAL school forms that you likely originally had to turn in to register child. Be polite and respectful, but firm that they must make this change to the 504 ASAP.
Next, I'd familiarize myself with how to document -- this is great website if you've never seen:
http://www.dphilpotlaw.com/html/record_keeping.html (Lots to explore there, besides this section linked to.)
THEN I would take the list of accommodations you believe are necessary and appropriate, given this child's needs and disability and I'd prioritize so you can work on them bit by bit.
Do you have this USDA form on file which would help so far as school lunches? (It requires doc help . . . )
Look here for that form link & detail as to page #s:
The USDA Form