Dr. Steve mentions home schooling. I used to work with these two fat chick's. They were a few years apart in age but we called them "the twins" because of their double chins and double bellies. They were both home schooled and were dumb as two dollar dogs.
They had two sisters that were thin. I asked once, "What is with your two sisters that are thin?"
The younger of them replied, "They are normal."
What??? And you are not?
"When bad men combine, the good must associate; else they will fall, one by one." Edmund Burke