I mentioned before my friends son has a peanut allergy, I also mentioned his school banned peanuts before he got there and not because of him.
The reason goes back a few years, the story is kind of convulated, but from what they told him and he told me, it had to do with a misshap involving the needle and a former student.
They story is kind of murky, from what I (and he) understand, years earlier another student had an allergy to peanuts, the parents told the school (but did NOT ask for a ban or anything, they gave the school an "epi-pen" for emergenices).
Here is where the story get fractured, the kid was either in kindergarden or 1st grade, now either someone gave him peanuts or a peanut product (that kids parents version) or someone had peanuts and touched him or exposed him (schools version).
Kid had a reaction and the needle was either misplaced, didn't work or something.
Kid lived but was hospitalized, there was a lawsuit, and yada yada yada.
School banned peanuts after that.
To the best of my knowledge outside of a few cranky parents, there hasn't been any problems in practise with the policy.
Cute sidestory: My friends son has a peanut allergy, but his older sister doesn't, but she tries to pretend she has an allergy to all vegtables.
It doesn't work.