My Mrs is a maths teacher, one of her main reasons for going into teaching was because her teacher at high school was terrible and often put people down with these kinds of remarks. She spoke about how she would use her as an example to the other students, making her stand at the front of class trying to solve problems in front of everybody, often way beyond her current level and for things that were completely irrelevant to the subject. Then putting her down when she obviously couldn't come up with the answers on the spot, it sounded like it was more of power trip rather than the little push to make them focus more.
Fast forward 15 years and the Mrs has become a successful teacher, pretty much waiting for a head of maths department role to open up. She was asked if she could help out and go into a couple of failing schools in the area as part of a team to assess how things were being done and provide training on areas that needed improvement. Lo and behold her old teacher was at one of these schools and had been put forward to receive some training from her
Apparently she still had an attitude and was very dismissive about receiving help, Mrs was well chuffed when she came home.