I would argue that none of us have "back in the day" circuмstances anymore.
I sent one of my children to an sspx boarding school. Worst idea ever. Learned about porn, perverts, uncontrolled internet access, bad language, bullying, and how to be sneaky among others.
They had a high-school graduate teaching 9th grace English, and a math professor who thought a child should not receive "A" grades if the child didn't show the work (did it in their head).
One of my nieces taught 5th grade at an sspx school when she had only just graduated high school.
Homeschooling is the only way to go.
There is no reason to think that a well educated high school graduate is not capable of teaching well.
‘Back in the day’, teachers’s college did not exist. My brother who is 5 years younger, tells me that when he started school he could already read because I taught him to read, so at that stage I would have been 10. I have no memory of this, but he swears I taught him and I believe him.
Mother Mary McKillop started a school in a stable which grew to be a great establishment, without training. You are either a teacher or you are not. Most HSing parents are not trained to teach, they just try and they do.
Teacher’s colleges mainly indoctrinate the students, can kill the imagination, and set them in a certain pattern which is hard to break out of.
I taught “untrained” in a mission school for two years and did well and loved it. Your own schooling, whether school-based or home-based, is quite sufficient, if done well.
My grandfather, a country boy and farmer, always wanted to become a teacher and so went back to school (I do mean school, not college/uni) and achieved his ambition. As he fathered 12 children, he would have always had one of his own in class. But of course he got paid for schooling his own. I remember him well teaching me how to spell Constantinople, breaking up into syllables and making it into a little jingle.