There was an excessively annoying kid in my high school and I learned to send remote commands to any computer in our lab, so I sent a command on loop that continuously opened his disk drive (it would automatically re-open after closing), and if he was particularly annoying I would shut down his computer.

I never once got in trouble for it - the teacher would ask the class, directly looking at me, from time to time to stop it, but I never got in trouble.

I imagine he was just using those announcements to get me to stop from time to time, but knew this kid deserved it so he never did more than that.