Gaming Network, Help

Hello all, I'm a first timer to this site, it looks really good by the way.

Anyway to my problem, I'm currently running a computer society in my college and I'm having a bit of trouble setting it all up. I have 9 computers at the moment and all have a fresh install of Windows XP Pro, and the drivers are up to date. The way we are trying to set them up is the have 9 computers all connected to a switch with one computer being a dedicated server for the games. We though this was working but got unacceptable lag on some computers when we tried to play some games.

I ran the network set up wizard on the computer we are using for the server and with the rest I manually set there IP's, subnet masks, default gateways and DNS server's. The computers can all see each other on the network thats not the problem......But how can i set this up so that all the computers can play the same game and not get any lag, well not get lag above 50ms.

If anybody knows what i can do to improve the performance of this setup please reply, also if you have any ideas on a different type of network i could use that doesn't cost to much please let me know