The only "explanation" I heard was that Robyn's kids to go public school, and they wanted them all to be together. Except the oldest daughter wanted to stay at the private school.
I was wondering about that too. The hierarchy in the family is odd. Apparently Meri calls the shots enough that her daughter can go to private school, which pulls money out of the big old pot for the amount of tuition. The homeschooled kids need to go to public school now because there is strength in numbers, that way Robyn's kids don't feel left out/made fun of as much? It seems that Meri and Robyn are the favorite wives. Hmmm....