In this analogy though, is 99% of the population able to eat and digest arsenic without a problem?

If so, I think the reality that needs to be dealt with is that there are going to be a lot of situations throughout their life where people are going to be serving arsenic. It sucks to be in that situation, but it's something that child will need to be taught to take into account (even if accommodations can kick that can down the road for now.)

If arsenic is poisonous for everyone in this analogy, then I have a lot bigger problems with this school than the lunch menu.