What "%" risk that your child would be poisoned do you find acceptable?
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.
Yes, if there is a substance that's poison for one kid, they'll need to learn to take precautions. And if there's a substance that's poison for all, it should be banned from school meals. What if it's 10% of kids? 5%?
Food allergies are common these days.
Your attempt at an analogy was clumsy and nonsensical regardless. They aren’t serving poison at schools. Sugar would have been a better example.
Would you send your child to school if there was a 1% chance that they would be served something that would put them in the ER? .5% chance?
If you were a school administrator, would you serve food that could put 3% of the student body in the ER? 6%?