What's the Hand Foot Mouth policy at your child's school? Does it help to keep down contagion?

Hand Foot Mouth is going around my son's school, and today reached his classroom. But the family of the classmate who has it told me if the kid doesn't get more blisters and isn't feverish, the school said they can come back tomorrow! The family seem to think it's no big deal and that since the kid doesn't have a ton of blisters, no prob.

Is that the norm, to be able return to school still full of fresh blisters?? My son hasn't been in school for a week with a pretty uncomfortable respiratory virus which I got too and it completely knocked me out for 7 days. He was going to go back to school tomorrow and now I'm like jeez is he just going to come back with Coxsackie and set off a fresh round of hell? Not sure if I should keep him home more days now with this situation.

Am I misinformed about how contagious HFM is? or is it just unstoppable, so they don't bother isolating the kids who have it? They are supposedly disinfecting the classroom every evening, but gosh...