I always bring up this story when talking about (bad) teachers. Once on my way back from school on public transit, I saw a teacher grading essays. They give this one essey an A, then close the notebook, check the name, open the notebook again, cross out A and write a B. Obviously I don't know the backstory, but I was still looking at it in disbelief. I'd definitely been graded lower based on how the teacher liked me. Even on things that should be objective, like science subjects.