The junior high school was having trouble with the seventh grade girls leaving lipstick marks all over the mirrors in the girls bathrooms. No amount of warnings or requests to stop helped. So the principal called the girls into one of the girls restrooms for a talk.
"You all may not realize how difficult it is for our custodian, Mr. Anderson, to remove these marks so I've called him in to demonstrate what he has to go through."
Mr. Anderson stepped forward with a long-handled scrub brush in hand which he immediately sloshed around in the toilet before using it scrubbing the mirrors.
There was never again a problem with lipstick marks on the mirrors.