Children don’t seem to care about germs, much :-).
They certainly have choices other than sitting on the lunchroom floor, though. At least they should have other choices. Maybe they can’t let them take lunch into the classrooms (as we sometimes did, especially in bad weather) because they’d trash the rooms or have orgies.
But it’s pretty clear they’re sitting on the floor - most of them, not all - because they’re shrinking the TOTAL lunch allotment. They’re having only 1 lunch period for everyone instead of 3 for 1/3 each, e.g.
So, they couldn’t eat in the rooms (if you require a “free-time” lunch) because those rooms are used only for class time. They’re not simply “open” rooms at lunch.