This is sounding a lot like a situation my family is now dealing with, and the results weren't pretty.
My sister-in-law attempted to homeschool her daughter. It's a bit of a mystery why, because it definitely wasn't the usual religious or political reasons. The sister-in-law did not do well in high school, barely made it to graduation. I can only guess that she didn't want her daughter to have the same terrible experience with school that she had.
The end result was that starting at age 11, she kept her daughter at home, did not connect up with local school districts while moving to two different states, and apparently went from minimal schooling at the beginning to no schooling at all. Which should not have been a big surprise since she did so poorly in school herself. Her daughter ended up isolated from other kids her age, mostly just sitting in a room bored out of her mind. The daughter is now 17, the rest of the family has intervened and she's finally getting enrolled into a good small alternative school, where she'll be assessed to figure out where she needs to catch up, but it's going to take awhile because we know she needs some refresher courses on multiplication tables, for instance.
So you have got to ask yourself and your wife hard questions about why she feels qualified to teach when she couldn't even complete high school. Maybe adult life and the GED stuff got her up to normal functioning or maybe even better than usual - but probably not. What happens in the very real possibility that she finds she can't hack it as a teacher? Because the ability to teach is not in all of us, and if it was difficult to learn, it's going to be even more difficult to teach.