Open source in schools how much sense does it make ?

What would be a "practical computer lab" look like for a school that has a batch of about 20 students.

Here are some thoughts about it.

1. There must be 20 computers.
2. There should be one central server ( in addition to the ones in 1 )
3. All these computers be networked.
4. Lets us get Linux loaded on these machines.
5. The central server will act as the file server , central authentication server, intranet server,
backup server.

following will be a few resources I wish to use

http://www.ghca.com/computers/

http://dansguardian.org/?page=smoothwall

http://www.go2linux.org/going-back-to-windows-get-more-linux-users

http://radar.oreilly.com/2008/05/teaching-kids-programming.html

http://www.schoolforge.net/

http://www.sugarlabs.org/index.php?template=page&page=learners