Here’s how I did it once a upon a time. Had a kid working at a company who was 20 something and always hitting on a couple of high school girls who were part time in the afternoons. Didn’t work for my department so complained from time to time. After realizing it was to no avail, I had some bumper stickers made and had one discreetly applied to his vehicle.
It read, “My girlfriend is an honor student at (name changed here) Elementary School. The idiot didn’t know it was there for two weeks and only discovered it after he noticed people were constantly honking horns and pointing at him.
Ha!