My high school had random drug testing. After getting selected multiple times in a row, I finally asked the dean if it actually was random. He said, "We don't know if you'll take a urine test or a hair test that day. So that's the random part. But we hand pick the students to be tested."
Creative, but I rolled my eyes.
Edit: yes, this was a private school
I went to a private high school and if they drug tested we wouldn’t have had sports teams. Too many high school kids smoke pot to try and punish everyone for it.