Korashime ~Kyouikuteki Shidou~

Main character is a Physics Teacher, 25 years old, single. He gets the news that he can go to teach at the university he was longing for from the start. At that time he occasionally eavesdrops girls giving scores to teachers in the dressing room. Then he is invited to a small farewell party where he gets drunk. The next day his embarrassing photos get spread in the class. The anger reaches its peak. Now the revenge is inevitable, but there's the need to plan steps carefully not to get framed.

[From vndbreview]