does your school give your computer a public ip address or do you all get private ones that connect to the internet via a gateway or proxy server? Does your school put you behind a firewall? What you are asking here you should be asking the technitions at your school because the answers we wont know. As far as configuring linux to be a server, lots of us would be happy to help. You failed to specify what kind of server and what you want it to be doing though... other than file sharing, which is easy via ftp.
