Unfortunately none of that fun stuff lasted very long. Mostly because word would travel and enough people would know about the things they could mess with. At a certain point is was basically assured that someone would do something exceptionally stupid and get the IT guy to actually figure out how to lock that shit down.
Though they never did figure out how we got local admin access to the machines[1]. That was a fairly large security breach actually... once you have local admin, installing a keylogger that drops its logs onto a hidden network share on the machine is trivial. Personally I stayed out of that because my dad would have murdered me if I ever got caught (the friends of mine who did it did end up getting caught!) Still, I found the local admin password was useful for tweaking settings.
[1] It was simply by dropping a disc in and booting the machines into a password cracker. Was very fast since it used rainbow tables.
Yeah, there were genuinely malicious actors. But there was also just plain old fun.
So many Windows 2000 machines in my school and I didn't know what power was at my hands...