[Onelifetogive]

home-schooled children consistently score higher on SATs and other placement tests than children educated by public schools.

Your definition of "teach" is different than their definition of "teach."

See "indoctrination."

[FourPeas]

My father had a Ph.D. in mathematical statistics. He wasn't considered qualified to teach high school algebra; he was considered qualified to teach elementary algebra, calculus, differential equations, statistics, etc. in college. It's definitely not about knowing the subject matter; it's about indoctrination.