Are you the head teacher? First of all, you should praise your children. This is the first step of communication. Second, you should tell her the truth euphemistically, honestly take responsibility, explain the problem, and ensure that the math will be corrected. Third, I hope parents can take care of their children's self-esteem and self-confidence and math teachers with you. You can talk to the old teacher about this situation, and then discuss both soft and hard skills with this teacher. You must correct this teacher's attitude.