Growing up I had a few instances where I was not at home and had ambulatory reactions. However, once I got to the ER they would not treat me until either one of my parents arrived or until I really started to "expire". What we ended up doing was having my doctor write a note saying I should be treated immediately, even if not ambulatory, and then my mom signed it and it was notarized. I kept it with me everywhere. It actually helped for one trip from high school in an ambulance (they put GROUND PEANUTS in dinner rolls to fulfill a health requirement! Mind you this was in 1990....)
Anyhoot - I would suggest getting a similar note for your child to carry with them and/or keep a second one at school.
------------------ 30-year old survivor of sever peanut/tree nut allergy