I know you can do that whe

I know you can do that when you edit. The other way is to have a switcher. This is a machine that swichtes from different feeds. It’s used for broadcast and live TV. But they are very expensive. A setup would be possible, but I don’t think you will want to pay the price. You can judge by yourself.

http://www.panasonic.com/business/provideo/cat_mixers_studio.asp

Other than that, the only solution would to have more than one computer and then the student wil open more then one skype or msn (like if it would be differnt people.)

Hope I’ve been helpful. Good luck,

Antoine