Given that they occurred in the 50s, 60s and 1970s I don't think it's unreasonable to assume that these experiences did not happen. It was common for teachers to hit children regardless of hearing status in this time period because corporal punishment was allowed. Even in the Catholic primary school I briefly attended in the 1980s, I can remember seeing a teacher having a temper tantrum, shaking a child by the shoulders and slamming him against the wall.
It never happened to me though. I was educated orally in the middle 1970s to late 80s and had for the most part nice teachers who didn't hit me or threaten me. They made it fun. In some cases, I was favoured and it made it a bit of a problem for me with the other kids. I did have some stupid teachers in the mainstream school who would talk past me, who treated me like I was a waste of time in music lessons (I retaliated by refusing to go to music lessons anymore) but mostly they were good and believed in me.
I personally think that it would rarely happen today due to the amount of legislation around today that protects the child.