I got stuck with a maths teacher in my second/third year of highschool who couldn't teach. Like, none of his students ever passed. literally NONE. it wasn't

I got stuck with a maths teacher in my second/third year of highschool who couldn't teach. Like, none of his students ever passed. literally NONE. it wasn't even a close thing. My grades went something like 70% year 1, 40% year 2, 32% year 3, 60% year 4, 75% year 5, something like that. I was one of the lucky ones in that my brother could help me with my maths work for those grades. I'm not joking when I say 1/3 to 1/2 the class would regularly get <10% on any given test. My parents(and many others) complained to the school. They couldn't fire him for a bunch of reasons I don't want to get into, beyond "south african public school". When people talk about keeping a child with one teacher for a long duration, I think about that maths teacher. It's like a democracy, rotating people in power around highlights problems, and also limits the damage of the bad ones. I don't think any teacher should ever teach any child for more than 1 subject for more than 1 year, in an ideal world.