Thursday there is a ladder on the left of the school entrance that appears once you have received an F, the first time you will see mabel stuck on the fence at 1900. Next week you must adjust the ladder to "punish until the scene ends on its own" (for the previous week), after this you will sneak into Emi's office (avoid the floorboard) to catch her the weeks following at 1900 (do not adjust ladder after the first time if you want to progress).