Ok guys and gals, my boss came to me and asked me to learn something on a Mac. I work at a school where in the computer lab we have about 25 Mac's running OSX. She wants to know if there is a way to lock up the Mac's while she is teaching so the students can't surf the web and all that stuff. If she is at her desk is there a click of the mouse or something that will turn this feature on and off? if so what does she need to do?