Is it a conflict of interest when a dance teacher has his girlfriend in the class as a student?

I used to take salsa classes with a very good teacher. He recently started dating one of his students. She now joins us during the class. It wouldn't bother me so much if it was subtle, but they joke with each other and she stares into his eyes. lol! It's uncomfortable! Maybe the guys feel different. I felt it was a distraction for me anyhow. He's not as focused on teaching, he's texting during class, and she even walked in during the middle of class, disrupting everyone, because they had a fight a few days before and she was trying to make up with him. Ugh!!!! I know love makes people act stupid, but please leave it outside! Don't you think you would downplay it or take class elsewhere? I'm losing respect for him and losing interest in class altogether. What is the ethical thing to do? I don't think the people at the dance studio care--they let a famous instructor do what he wants. He flirts a lot with the students too.