why is it all right for 500+ people to gather in schools

Because the kids show fewer symptoms, if at all and they need to infect as many people as possible under the herd immunity plan, which it sounds like is unravelling but may take more time to unravel completely.

It's eugenics, pure and simple. The poor are inherently inferior and deserve to die, as do disabled people and in some cases, the wrong kinds of ethnic minorities. This isn't even a new policy. This is being handled by the people who designed, implemented and persist with universal credit, who designed, implemented and persisted with the hostile environment that led to British citizens being deported to and dying in Jamaica for the crime of being Black.