What sort of data do you expect? You can't compare the psychological impact of teacher X's confrontative behaviour towards parent Y with that same teacher X's behaviour towards the same parent, but now in cooperative style. You can only research the situation in certain schools before and after you run a programme teaching teachers to establish cooperation with parents. If you are really interested, I could probably recommend books (in German mainly), both with the angle of teachers' cooperation with parents of pupils, and not unrelated, cooperation between social parents and birth parents. Here respect towards the birth parents is even more vital for the children's self-respect (and more difficult to maintain).

If your childhood friends say something else, I wonder how old they were when the confrontation took place. And did they tell you about it with the distance of adulthood or then, as youngsters compelled to be "cool"?