Since this question is already answered, i'm gonna tell you how "i think" students can still cheat :)
At usek, they have all kind of stuff in their labs, so i was taking some course about some stuff, and they used
citrix I had an account on their servers, only some software were installed, i was only allowed to use IE which makes me crazy! i hate it, i wanted to install chrome, didn't have the privileges, But that wasn't a problem at! thanks to Portable apps! i downloaded chrome portable and many other software, it felt like home sweet home!
Portable apps aren't installed, think about it like swf files or jpegs, there's no way for the pc to stop you from using them.
You have 2 solutions to stop users from doing what i did:
1- Configure your firewall to stop your users from accessing popular websites where they can get their hands on portable apps, such as filehippo, cnet portableapps.com...
2-which is a simpler solution,
disable firefox download manager, this can be bypassed but i don't think anyone would do that.