There's a lot we don't know.

What country were these people from? Where was the girls' mother? Were the healthy children boys or girls?

There are countries where, if the other two were boys, then starving the girls and clucking the tongue when they "died of pneumonia (or whatever)" would be considered normal behavior.

There also are cultures where, if the father took the girls away from their mother, then she has absolutely no rights in the matter and no one will tell her where they are. The father could be mistreating the girls in order to punish their mother.

As for the schools, I think we can assume that if they were being kept in a basement, then they weren't going to school.

I'm just so glad that someone sent in the tip and that the children are out of there.