I once worked with a Head of Mathematics who frequently stormed into the staff room declaring his students to be thick. I remember one occasion when he said that he had explained a concept three times to them and they still didn’t get it! I thought of him when I saw this image.
The same teacher used to describe himself to parents as a Mathematician. He wasn’t a mathematician any more than I was a historian. Had he been a mathematician he would have been researching in a university. He wasn’t, he was teaching in a rural school. He was “a teacher of mathematics” and like all teachers, his effectiveness hinged on his communication skills and creativity.