Saved by the Bell: The New Class (1993) : 3x11

The dreaded teacher ""Wicked Witch"" Hurst is giving one last killer physics test before leaving the school. Tommy breaks a date with Lindsay to study, so Ryan jumps in and takes her out instead. Later he spends half the night talking to her on the phone. The result is that Ryan has done no studying of his own, so he convinces Screech that it's ""National Fire Drill Day"" in order to get out of taking the test. The sprinkler system goes off and all the Homecoming floats in the gym are ruined. A new teacher, Mrs. Rumplemeyer, takes over the class, and she's even tougher than Miss Hearst. It turns out to be Mr. Belding in drag, trying to teach Ryan a lesson. Ryan works to repair the damaged floats and when Lindsay asks him out, he declines--he has to study.