It's kinda horrible that your "co-teacher" would say something like that to a student. If it makes you feel better, in college I had one professor stand up in front of the class and say that all the people at the back of the class were stupid, didn't deserve to be there and they were going to flunk out. I was at the back of the class. I did rather well in his class actually! :) There is hope that the power of suggestion might sometimes be taken as reverse psycology!