" don't have access to the training resources given to the school teachers, or understand the subjects being covered, home school is for naught."
I disagree. The parents don't have to be great teachers of every subject. Just showing their interest in their kids doing well in school can be huge.
After my parents divorced and my mom went to school to get her nursing degree, we turned her coursework into a dinner time contest. I wound up doing better in her chemistry classwork at age 8 than she did. It was a game to try and get ahead on her lessons. I still know the periodic table well from memory from all of the drills we did. She wasn't teaching us, we were her flash cards.