so, yes - some fraction of a percentage of kids will die when they open the schools. if ifr for kids specifically is .05% (a high estimate), and 40% of the kids get it, then you should expect that 0.02% of the kids will die. very simple math.
but, that's a not a high number, and only the most ridiculously risk adverse people would see it as a reason to halt.
kids get sick from something they caught at school and die every year. kids are robust, but they're fragile; they die easily.