I definitely used my shitty old watch to cheat in freshman high school english. We still had spelling tests, but the words were intense. I had a rubber watchband and discovered that you could write on it with pencil lead, but it would wipe off the moment you touched it.
The only other major cheating I ever did in school was working in the engineering building until ungodly hours of the night, and finding computers that seniors abandoned without logging off. I raided every one of their network drives and had copies of notes and lab reports for all future classes.
I almost got my ass beat once for selling “Secrets to getting 100% on all upcoming tests”, burned to CDs. They assumed it was cheats, like answer keys, test questions, etc. It was actually just a single text file, containing a single line that said “Study real hard.”
Charged them five or ten per CD, made a decent whack of cash before the teachers (rather reluctantly, they thought it was funny) stopped me.