The teacher was annoyed by a classmate. What message should I send to comfort him?

Hello, dear. If you have a good relationship with your teacher, you should give him a tissue or tell a few jokes to make him laugh.

On the premise that the teacher is a woman, it is best not to do it in front of many people, or be known by many people, otherwise you may be isolated or bullied.

If it's a male teacher, I don't think the other person will need your comfort.