I had a horrendous primary teacher - an unmarried older woman, who would yell and scream, take children by the scruff of the neck and throw them around, chuck blackboard rubbers at us, etc. Everyone was petrified of her.
All my mother ever said, when I told her any of this, was, 'Poor old thing, I expect she lost her boy (friend) in the war.'
And at a parents' evening, I saw her all pink in the face, smiling and positively simpering at my father, who was goodlooking and extremely personable and charming. I can still see her face now!
Despite all I'd ever told him, he said afterwards, 'Oh, I thought she seemed quite a nice old thing.'
I had never felt so betrayed!
But it was a good lesson in how easily people can present quite different faces to different people.
I'm glad to say that at my senior school there were some excellent teachers as well as the average - no bad ones at all.