ok thanks to all the answers they helped ME a lot. But i would suggest none of them as an solution for the person who asked the original question. All mentioned tools require to much work for the purpose to test students code as a teacher,tutor,prof. The best way in this case would be in my opinion virtualbox. Ok, its emulates an complete x68-system and has nothing to do with the meaning of sandboxing in this way but if i imagine my programming teacher it would be the best for him. So "apt-get install virtualbox" on debian based systems, all others head over to http://virtualbox.org/ , create a vm, add an iso, click install, wait some time and be lucky. It will be much easier to use as to set up user-mode-linux or doing some heavy strace stuff...
And if you have fears about your students hacking you i guess you have an authority problem and a solution for that would be threaten them that you will sue the living daylights out of them if you can prove just one bite of maleware in the work they give you...
Also if there is a class and 1% of it is as good as he could do such things, dont bore them with such simple tasks and give them some big ones where they have to code some more. Integrative learning is best for everyone so dont relay on old deadlocked structures...
And of cause, never use the same computer for important things (like writing attestations and exams), that you are using for things like browsing the web and testing software.
Use an off line computer for important things and an on line computer for all other things.
However to everyone else who isnt a paranoid teacher (dont want to offend anybody, i am just the opinion that you should learn the basics about security and our society before you start being a programmers teacher...)
... where was i ... for everyone else:
happy hacking !!