I was a school-district computer technician. On a few occasions, I had to dig into district computers, to see if they were being used inappropriately. Unfortunately, I did find one guy had been using his work computer to visit dating sites, although it appeared he'd never joined one -- just looked at them. An administrator wanted the guy gone, so she used that to nail him.
On another occasion, I checked into the system of a very popular teacher, who'd just been hired away from the district. Turned out he spent a lot of time on a site devoted to wild parties, with a lot of nudity. Happily, since he was gone, I was able to quietly wipe out his browsing history, etc.
One time it was a pleasure, though. Around 2002, some wise-ass kids changed the BIOS in a lab computer to make obscene comments about their substitute teacher (She really was nice gal and didn't deserve the comments). One guy admitted he'd taught the others to make the BIOS change (they'd removed the BIOS battery and reset it so it wasn't locked). He was pretty belligerent about it, saying he wasn't guilty of anything as he hadn't done the actual changes.
So, I dug into his browser history, etc., and found that computer had been on a porn site whilst he was on it. Turned that info over to the Vice Principal...the kid wound up sharing detention with his buddies.
F