I suspect schools will be only left open for the kids of 'essential workers', been doctors, nurses, health professionals etc (whilst the rest of kids will get home schooling). Why, I guess a calculate drisk by government that they need to do this because you don't want over 20% of your health workers coming off line. As to the question in the post, given I suspect the majority of children (over 90% in a school) will be home schooled, social distancing etc will happen in teh school by the fact of low, very low, turnout given mos workers are not deemed 'essential workers'.