In the upper grades, homeschoolers often teach themselves, just like college students do, and just like most government high school kids actually do.
There are plenty of on-line resources to fill in the gaps. That's what my daughter did, even though I was qualified to teach her. I did help her out from time to time, but she often corrected me.
Have you ever learned a software program by reading the manual? I was shocked when I learned that a software program that took me a week to learn, and be functional in, was offered as a semester-long course in art school.
Think of how focused children would be, and how quickly children would learn, if their courses were modularized, and where they could advance after passing a test. They wouldn't just sit around killing time.
I noticed this with my homeschool kids. Once they learned that they could go out and play after finishing their assignments, they got down to business, and finished their work quickly.
Sure, there will some kids who will be smart enough and motivated enough to learn by themselves. That’s always been true. But I haven’t still haven’t read anything to make me believe home schooling will be adopted by the great majority of the nation’s families.