It's shutdown -s -t 20 -c "Shutting down for administrative purposes"
Why do this when you can access the entire network and have a chance of getting in? Just follow below:
Download ProRat, search it on google to find. Now, after you install this, go to 'My Network Places' and on the side of the window, the bar should have a bunch of quick links, click on the 'View Entire Network' one. Then, just simply find one of the computer's network file, probably the one sitting next to you. Before we continue, download a FILE-FORCE program, meaning a program that forces a file in a certain directory, and force a ProRat virus onto the computer next to you. Then, tell your friend to logoff that computer, make sure you have ProRat running, and get the teacher to log him back in. While he logs in, keylog him and get the password, which is probably the master network password or something. It's pretty simple when you get down to it...=)