If you are just trying to connect them to the network (and not bind them to the server) and the machines won't get a valid IP, the network might be configured to not hand out DHCP addresses; a school system I worked for in the past had this sort of setup to help deter people from connecting unauthorized machines to the network. You can check this by looking in the "Network" panel in the "System Preferences" of a working system, clicking on your ethernet connection and taking look what the pulldown menu says right next to "Configure IPv4". If it says "Manually" or "DHCP with manual address", your server is most likely configured to either not hand out addresses or only hand out addresses to specific systems.
Another thing to note is that if, on the non-working machines, the ethernet connection has a red icon next to it in the Network pane after plugging it into the wall it is not getting a link to whatever switch is at the other end (assuming that the jack is even connected).
In order to allow user authentication/login to be delegated to the server, you'll need to bind the machines to the server so the users can login (you'll need to get your network issues resolved first, of course). Before I can give you much information here you'll need to figure out several pieces of information:
- What is the IP/Domain name of your server that you want to bind to?
- Is it a Mac OS X Server or Windows Server?
- What version is it running?
- What version of Mac OS X are your clients running?
- The CN you're going to bind to
If you don't know any of these (or only a few of them) you will need to talk to whoever setup your Mac OS X Server install to get them.