Joseph- I disagree with you here. It takes a lot of planning but it can be very rewarding. Your kids can end up smarter and ahead of their grade-counterparts and they learn many skills like perseverance and individual work. They also gain an inner drive to work by themselves and for themselves. They can really gain an interest in the subject matter and if they are able to help pick some of it, they will be even more interested! (like american history, state history, world history ect and can concentrate on aspects that they are interested in, not what the teacher likes).
It is a cheaper alternative that can reap fabulous results. The parents dont have to do the teaching themselves as long as there is one parent per level. Or you can join similar levels together for subjects that it doesnt matter what age they are and give different assignments on the topic.