You can do that easily
there is just not enough time and its easy to get caught
There is no bios password
I changed the entire time and crap on my schools p.c for kicks and giggles.
It was easy to do everything and anything else.
Only thing is, the students all gather and make a big deal of it and thus it gets noted. And you get a teacher detention.
This. No BIOS password and having a Linux distro running on your screen is too obvious. We need to be able to just minimize Windows and pretend to do our school work to get away with it.