If I had a child who was that allergic, I wouldn't make his life someone else's responsibility. You just can't expect that no one in the school will ever bring peanut anything. Even if the principal sends Patty-the-PBJ-bringer home immediately, what did she touch before she left? If you read labels, peanuts are EVERYWHERE.
I don't like them, never have, the stench of an open jar of peanut butter used to drive me from a room, but I'm not allergic. I never thought George Washington Carver did us any favors proving they were edible.
I agree completely--and I've got one of these odd allergies myself. My parents never demanded that the school impose restrictions on everyone else because of me. You know why? Such a thought never even crossed their minds. If someone had suggested it to them, they would have rejected it as unthinkable.
Things sure have changed since I was a kid. But the fact remains that it is my responsibility to read labels and ask about ingredients when I am in a restaurant. The responsibility of the food industry or anyone else ends with accurate disclosure. It's not their job to insulate me from my allergy when that means denying a perfectly legal class of foods to people who have a right to eat it.
We could go the next step, and just lock them up and throw away the key.
My friend didn't have his kids school ban peanuts, they did that from a prior lawsuit where someone got hospitalized.
However, it was smart, and it made sense, and since then, they haven't had any problems.
As far as I know, they don't enforce the rule with punishments, but with confiscation and a note home to mom and dad explaining the rule, I don't know if they make kids wash their hands or not, or other details.