Ubuntu :: Removing All Files From The Current Session?

I have just manage to set up a number of computers using NComputing thin clients. I have set up 5 user accounts.People will be using these account randomly. So what I want is to set up everything as it should be and that to be the default setting. If users download files or make changes to the files these should be for the session. On startup/shutdown all the files and changes should be deleted this way the next user can find the machine clean. And also there is limited maintenance to be done.