A number of 12-year-old girls were beginning to use lipstick at a private school. They would apply the lipstick in the restroom. After they put on their lipstick they would press their lips to the mirror leaving dozens of lip prints. The custodian would remove lip marks from the mirror each night. The girls would put them back the next day.
Finally the principal decided that something had to be done. She called all the girls to the girls restroom and met them there with the custodian. The principal explained that all these lip prints were causing a major problem for the custodian who had to clean the mirrors every night.
To demonstrate how difficult it had been to clean the mirrors, she asked the custodian to show the girls how much effort was required. He took out a long-handled squeegee, dipped it in the toilet, and used it to clean the mirror.
Since then, there have been no lip prints on the mirror.