In the episode where the kids get the measles, they are all sent to walk home with fevers.

Shouldn't the school have called home and had the kids picked up?

Back in those days probably not. I went to school in the 80s and on a snowy day the bus would let us off a mile from our house and we would walk in the snow to get home. That does not happen today and parents freak out.
Back in these days a complete stranger could go to school and sign a kid out. So I dont think it would be that unusual to send kids home without telling their parents. Sounds crazy by today's standards but in 1970 not that unusual.