The first I learned of lunch swapping was in high school on TV. I never swapped back in grade school when I actually brought a lunch.
I packed my own lunch everyday...so it had what I wanted - no need to trade.
I used to buy lunch at school (back when you actually had to BUY lunch), but the kids who carried their lunch were always swapping stuff. Big deal. If I had kids today, there is no way in h*ll they would go to public school. If a kid has allergies, it is the parents' responsibility to teach them about it and let the teacher know as well. Life-threatening allergies are extremely rare, percentage wise. Why should all the children have to lose their freedom to protect the collective bureaucratic @ss of the state?