Incorrect.
The children of key crisis workers will still be able to go to school. However, this is a relatively small number of children so only a small number of schools will remain open to accommodate them and the children will be "pooled" at these selected schools, so it is likely that such children may not be going to their usual school. It is not the case that most or every school will remain open .
This into is from Mrs D who is deputy year head at a very large school and who gets her information direct from the DfE.
My eldest is deputy head of a 600 children secondary school, he suggests 25% of kids, is is more than just those you mentioned, according to his information, special needs, in care etc.