It's not worth discussing, and I didn't really figure this out until my late 20s.
The first teacher was a science teacher that I had for four years.....who absolutely prevented evolution from coming up in the class. I actually figured her tactic of skipping chapters (she'd start the year on chapter 6, then go to chapter 4, then onto chapter 16, and so on). At the end of each year....the one single chapter on evolution would have been quietly skipped.
You can laugh over this today, but it's just remarkable this occurred each year.
Getting knowledge across? No....you eventually figured out that memorizing about 25 things for each test....was the only way of passing. After that....you would forget everything taught. She did a remarkable job in making you hate science.
The second teacher situation was a series of math teachers that the school had over a four-year period (the old gal had health issues and was gone mid-way through the 6th grade, the gal for the same class for the 7th grade stayed one single year, same for the 8th, and 9th grade).
None of the four seemed capable of getting a simple problem across to the majority of the class. It became a root-canal-like experience sitting there daily.
This was the early 70s, and these were mostly people who'd passed out of the college system in 1950s/early 1960s.
If you'd just gone to a self-taught or occasional seminar system? I probably would have been ready by age 15 to test-out and progress out of high school. I think a third of all kids are capable of that level (even today).
The fact that probably a quarter of all kids are low-IQ and just see school as baby-sitting? Well....yeah, that factor is driving a lot of this poor quality business that you see.