We all are teens around 14 and 15 years old in my class but I am only gonna focus on my friend, the teacher and I. I am gonna give fake names: my friend is "Lucas" ans my teacher is "Jack". So we had this teacher for the first time, at first he looked friendly and passionate but it quickly changed... He started being kinda mean to us but mostly with Lucas for no reason. Lucas is the funny but still good guy in class, he makes jokes but still works and does not disturb our lessons. There were no reasons for Jack to take him as his victim. We once saw Jack's screen on the interactive board, there was a picture of his children. Lucas said :" Oh, your children are cute and beautiful!" To which Jack replied:" Yes, I was lucky not like your parents". I saw Lucas laugh but that really touched him. The year continued the same way but no "big clashs" like that. But one day, Jack said something that really pissed all of us off. The window was opened and we heard someone screaming :" SON OF A BI*CH!!" and Jack had the wonderful idea to say:" Oh Lucas. No nothing, I thought they were calling you." We all were stunned by what he said as he started laughing. One of my other friend (Carol) who is always talking and laughing was not saying anything. Jack said:" Oh, come on Carol. You are always laughing but never when I joke" A JOKE excuse me?? At the end if the lesson, I went near Lucas and asked him if he wanted to go to the principal with me. He said that he didn't want the situation to evolve. That is the point where I may or may not be the asshole. At the end of the day, I had my grandmother on a call, I explained the entire situation to her she got mad and told me she was going to tell Lucas' mom. I told her I was gonna prepare the text and she'll send her. The day after I believe or IDK when I received a snap notification from Lucas. He told me he was so happy I said it, that he would never have dared. He was thankful. He and his parents reported Jack to the headmaster. Teacher had nothing but his behaviour changed. I think he knew I told it but I couldn't care less. I hate wrong behaviours of that kind. So, AITA for reporting that teacher?