A big part of the reason for the high scores is that home schooled kids have exceptionally knowledgeable and talented faculty.
That is not necessarily true. My kids knew more in junior high than I graduated high school knowing.
Homeschool parents don't need to be smarter than their kids. They can learn as they go too. I did. And I'd lay money on the fact that every homeschool parent on this board would say the same thing.
This idea that parents need to know everything before they can teach it is a totally fallacy. My kids and I learned some stuff together as we worked through the lessons.
Just because they are adults, doesn't mean that the parents can't learn too.