Just heard about this and have thus not tested it myself, but it sound nifty..
From the website;
It is hard to teach a group of people how to use a PC, or even how to use a specific program on a PC or the internet.
Yes, PC or web training isn’t easy. For someone who’s doing something right, there are probably two others doing it wrong, playing games, checking email, shopping…
Classroom Spy lets you see what everyone’s doing – without leaving your desk. You can monitor the activity of all the PCs in your classroom remotely. Plus, you can share your screen with your students’ PCs, making demos and presentations much easier.