Victor, you bring up an interesting point! “If you want to know how good a teacher is, don’t examine the teacher, but his or her students”: You would have to see all of the students to get an overall view, because let’s face it, all of us teachers have had a few students who really don’t represent our teaching. Either they had such a mind of their own that they play completely differently than you taught them to, or they didn’t listen, or they went to so many different teachers, etc., etc. It reminds me of the story about a famous violin teacher (Kreisler, maybe?) who heard a piece of his being played very badly by a busker. He went over to the man, took his violin, saying,”No! You idiot! It goes like this!” and played it correctly for him. The next day, he walked by the busker, who now had a huge sign beside him, with the words “PUPIL OF KREISLER”.