I understand cheering for the protagonist but saying that the only asshole is the male teacher does not give you a complete vision of the story, each character acts according to his own point of view and the information he has, and everyone is selfish. The protagonists risk get into serious trouble and maybe they need someone to get in their way to keep their feet on the ground, this can be done with good intentions albeit clumsily. Who love you do not always indulge you.
Does he have a romantic interest in the teacher? It seems so, but she also seems to be close to his heart as a friend.
Why did he talk to a boy? Well, have you ever had a friend who was in a dangerous relationship? She will never listen to you, in these cases they don't listen to anyone, it would be better look for other ways or do nothing