I don't know anything about the legality or ethics of taping a classroom but common sense tells me it shouldn't be a big issue. I think you underestimate what you refer to as "laypeople." If I heard a tape of what was happening in a classroom, I think I am quite capable of comprehending the fact that you are coming in on the middle of things that may have begun earlier. As for a teacher's role, I think you underestimate us here too. Anyone who is paying attention to the news these days, knows what is happening in schools. Oh, BTW, my baby brother has been teaching 20 years in an urban district in the worst school in the district. Last year an administrator was attacked with a chair (by a parent!). This year a student wrestled a security person down and tried to wrest the gun from the security person. There are so many incidents, I couldn't begin to name them all but I am well aware of what kinds of things happen in schools. Try not to think we are so dumb! Frankly (no offense to you personally), I think a lot of teachers are pretty incompetent, unintelligent, and even, downright ignorant. I give you all the credit though because it's not like it was when I was a kid.
I don't know why you seem to be going off on me. You can't
legally tape a class without the permission of the instructor and/or the administration. If you do it secretly ,and it damages the teacher in question by becoming public knowledge, you are liable. This is common law in lieu of common sense . All I am doing, is suggesting you don't mention the taping to the wrong people or you might get your arse in a sling . If you don't believe me , ask a lawyer .
BTW, I never said you were "dumb" . I realy can't figure out why you made that statement . However there are things in education you are not aware of as you were never a teacher . I feel for your brother also . If he was smart he would try to transfer out of that hellhole while he still has a mind . The conditions he is teaching in are the main cause of early burnout and depression in teachers. I have even advocated that select teachers in a building should be licensed to carry . They would have to pass a psychological and training The teacher(s) in questiion would not be identified . People would think twice before trying to take over a school building like they did in Columbine and elsewhere.
Good luck with your quest . The teacher in question has so much insecurity that he probably will not be around too long anyway .
Merry Christmas !!