Someone laughed at my child's poor grades. How should I answer back?

Find the weakness of the other family and fight him back. For example, their home is a mess and they can't get in; Cooking is like pig food, you can't eat it, and so on. The ruler is short, the inch is long, everyone has his own advantages and disadvantages, and we can't insist on consistency. Of course, improving children's academic performance is the best way to answer back.