Should I get revenge on my teacher?

[Yoshe]

this is a tough one. Was he otherwise a "good" teacher? Either way, as a teacher myself I am very careful what I post on fb. It wasn't child porn. . .so I don't think you can incriminate him.
I suggest you just leave it. The teacher realized himself that it was wrong and erased it. I think such revenge could sometimes come back to haunt the revenger. If you want the best revenge. . .invite him to a piano concert you are doing so he can see that you actually can play the piano. If there is no concert, pay a visit to the school and confront him about that day and ask to play for him. He may even apologize to you.