What should I do as a monitor (Grade A) (Grade 6)?

You can write him a letter anonymously and tell him about your current distress. When you get to school, try to be the same as before (if you treat him like a stranger these days). I believe he will come back to make up with you after reading the letter and really understanding it.

If all the above fails, there is another way. Your team leader should be conscientious and let others give you a thumbs up. When he sees it, he will naturally think that making you the team leader is the right choice, which will make him swallow this tone. Of course, when you are hated by others, you naturally live happily every day, making him feel that this trouble can't find you. If you are sad, he will naturally feel happy. "My snubbing method has succeeded."

So, you should live happily every day. Let him admire you completely. Don't make him unconvinced.