That sounds like a really stressful situation! I'm sorry that you aren't being listened to.
Here's what I suggest: interview your classmates about the worst things they can remember the teacher doing. Take written statements, better if it is in their own handwriting, and promise you won't reveal who wrote what. Just have them write the stories out without attaching their names.
While recording the teacher being rude would help, there are some specific laws about recording someone without their consent. If you were to go that route, I would suggest recording very secretly, showing only your parents but also demanding that they not reveal the recording as reason to pull you out (if they decide to do so).
The benefit of the written statements of multiple anonymous first-person eyewitnesses is that it is harder to deny than the words of one person, is entirely legal, and also protects the identities of others so they are more at liberty to lend their stories without as much fear.