Well, in my opinion an ideal teacher never lets the limitations of her children restrict their vision. She constantly motivates them to reach ahead and broaden their horizon. Criticizing a child infornt of others -I totally disagree. She should try to encourage the children and refrains from criticizing them. The perfect teacher prefers to give positive motivation to her children. I don't know what prompted you to post this, if you are experiencing this issue with your child, then why not you be frank with the teacher and give few guidelines on motivating children. Don't be afraid to voice your opinion after all its your child.
I think the teacher needs a mentor. Approach the management of the school