Happened to me as well, I had this one teacher for chemistry, she was a fucking nightmare. Easily my most hated class, and nobody had any notice of how bad she was because she just came back from a military tour and nobody that remembered her was in the school to warn us. She wasn't necessarily bad at teaching, like she knew the content that she taught, she just hated teaching with a passion.

Her class wouldn't have been that bad except for her grading. She would just straight up give failing grades on assignments for no good reason, doubly so if she didn't like you. She didn't like me very much (the feeling was mutual). As an example, we had a worksheet that involved some calculations and I got a 30% because I used an abbreviation for Avogadro's number when all of the answers were correct and all work shown. My lab partner who copied my paper got a 70, naturally. But one time she assigned this massive project where we had to watch some movie and write an analysis on scientific accuracy. At this point, I 100% did not give a fuck anymore so I just copy/pasted the plot from wikipedia and bullshitted the analysis bit in about ten minutes. Didn't even come close to meeting the length requirement...

...and I got a 100. Turns out, she was too lazy to actually grade the project and was tired of people complaining about grades so she just gave everyone who turned it in full marks. I'd have been really happy if I didn't hate her already.

Funny thing is, despite all the complaints about her, she just got a promotion and teaches the AP Chem class. I believe that of the 15 students that originally signed up, 4 are left, at least 3 of which are only still there because all the other Chem class spots are filled. She is literally un-fireable haha.