Our religion (Catholic) requires that we attend Mass or suffer a mortal sin. If those "Catholics" do not believe that, then they should not be Catholic. It's as easy as that.
When I was Catholic...There was mass on saturdays for the lazy...It was celebrated by a different priest than on sunday mornings. Perhaps these parents were going on saturdays...
I am not making the arguement for the parents. I think it is wrong to boost kids out of a class, even if it is all the "Jesus" they get.