I'm less certain about what secondary schools will do because there's considerable (medically misguided) pressure from parents to keep them open.
In Belgium one of the reasons not to close primary and secondary schools is that the children (certainly the younger ones) will have to remain at home under supervision of their grandparents, or they stay at their grandparents homes, as there are lots of dual income households. Just taking out the infected children and quarantine them is still the guideline.
A related recommendation is also not to let children visit grandparents and vice-versa.
As of this morning gatherings/festivals/... of 1000+ participants are forbidden to slow the spreading of the virus as stopping it is regarded as almost impossible without a huge economic cost. The focus is now on slowing the spreading of the virus to lessen the burden on hospitals and medical workers.