Few years ago, I read a manga about a delinquent girl who was the boss in her school, but she had to transfer. She decided to act like a normal girl in her new school, but it didn't really work out for her. Her romantic interest (?) was a teacher who is also her childhood friend, I suppose. I can't really remember any details, but I would be really happy if someone could help me. Thanks!

Sounds like you're looking for Oresama Teacher?

Ah, seems like it! Thank you 😀