Hi R.! It sounds like you need to call the school. There is no reason why you shouldn't be able to send your child to school with a lunch that has a pb &j.
My youngest packs almost all the time. She likes the uncrustables (either grape or strawberry) a juice pouch, a small bag of chips, fruit and a snack in her lunch. She likes the uncrustables because she puts them in her lunch "box" frozen next to her juice and it keeps it cold. She always buys milk at lunch as well since they don't sell the "big" capri sun juices any more. If they told me she couldn't eat pb&j she would starve all day! She doesn't like any kind of lunchmeat, and only buys once in a while when they have something on our menu that she likes.
Our school started going "nuts" nuts last year. We aren't allowed to bring any treats into the schools anymore...no birthday cup cakes, no cookies at Christmas or candy at Halloween. Our school district said it's because of nut allergies. I know they have a "nut free" table in the lunch room for the younger children. I know that food allergies are very critical in children....but I wonder about how much all the other kids have to miss out on because of a few kids that have allergies.....