If my diary is read and I am a classmate, they will tell my secrets everywhere. What should I do? I don't want my secret to be known.

Don't think too much, even if you hear it, you just think they are saying something that has nothing to do with you. Remember, the more unwilling you are, the more happy you are, because people who want to see your jokes are waiting for you to look decadent. I hope you are strong, even if the gossip is fierce, it is not as strong as your own heart!