My school is peanut/tree nut "free." No peanuts or tree nuts in the building.
However, we don't have a cafeteria currently and students eat lunch in home rooms and teachers have students clean up after, to varying degrees of actual cleanliness. Therefore a student could eat a PB sandwich at a desk at lunch, not clean it properly and a student with an allergy could end up sitting at desk next period.
Yeah, imagine how fun that is for me
I had a student have a reaction sitting next to another student eating peanut butter. The student wasn't upset about the other student eating it, nor was the parent, but we had to think about getting the allergic student a safer space. So if student's normal lunch spot might have exposure, student is allowed to eat elsewhere and take a friend. But this student is in HS and both Mom and I realize the world isn't allergen free and how we can get student to have practical, safe practices. This includes my teaching student how to give a Epipen to themselves if needed.
I feel like it is more my place to teach a student how to manage their allergy in both school and the world outside of school then spend my entire day policing the policy. It is there. We make sure any food we provide, including the school lunches we get delivered, are tree nut and peanut free. What else can one do?