Both of my children were taught by an educator without a degree until 6th and 9th grade. Both entered the private school system/public school system and have scored two years of perfect grades so far.

We were a pretty laid-back home schooling family. My kids didn't spend all day nose-in-books, watching documentaries in the afternoon between violin, piano and Spanish lessons. Up until this year it was a closely guarded secret how much time my kids spent "in home school." Had I let my family or non-homeschooling friends know how much actual formal class time there was, I would have probably been derided as a terrible parent. Now that they're sailing through school -- not just doing well, but generally underwhelmed by the difficulty of the material -- I'm not so shy.

They had, on a really good day about 2 hours of actual, formal, class-time with homework. The vast majority of the time, it was under an hour of mom-led learning followed by under an hour of homework, done in one room, alternating kids between homework/study but often times with both kids participating in each other's lessons (why not?). Aside from having to be single-income, and except for the "they're your kids so they aren't as easy to teach" problems[0], it wasn't difficult at all. Hell, the vast majority of the time -- especially since I work remotely -- it was downright awesome.

The above paragraphs might make it sound like I'm saying "Screw Teachers, their job is easy, any idiot could do it!" Obviously, it's much easier to teach two children than it is twenty-ish. Obviously, being that they're your own children, you have lack the complexity of dealing with parents, administration and politics. The reason "it worked for us so easily" is almost entirely due to these factors. I think about how, one year, we decided to ditch the math curriculum we were using for my son -- he was struggling, we found something better for him and within a week he was enjoying learning it. Having just the two kids meant we could make sure they were enjoying learning. When kids want to learn something, all you really have to do is point them toward "how." You're not going to get 25 kids -- some who come from tough home situations -- to all enjoy learning.

That said, I've never understood why (at least in the past) substitute teachers[1] never required degrees and were plenty effective, homeschooling is allowed without restriction, registration, or any requirement to prove you are actually home schooling to teach from a book basic things that every adult -- at one point -- learned. That sounds dismissive -- I'd imagine the vast majority of the job isn't that, and I have no interest in becoming a teacher because of those factors (difficult children, parents, administration, government) but I'd be willing to bet there are a lot of very qualified adults who would, but can't, because of degree requirements.

[0] My daughter was famous for breakdowns during math lessons. She can be emotional, but trust me, she's not breaking down in front of her Math teacher at school, today. Incidentally, despite her claiming to hate math all throughout home-schooling days, now that she's past Arithmetic, it's her favorite subject.

[1] Yes, most of the time, that's a single-day activity. We had one for three months, once.