We have a LTSP lab setup running on Ubuntu. We run the lab in a setup where the server does Authentication, Authorization and Accounting (AAA). Most applications run on the server. The heavy ones run on the client end. The lab supports 33 simultaneous clients in a "low-fat client" configuration.
This setup works well because the clients are 2.6 GHz dual core machines with 2GB RAM. One can run full HD Youtube videos via Adobe Flash on all clients and it still doesn't overload the server. The "server" itself is a [hand-me-down] Dell Precision 670 workstation with dual Xeon and 2GB RAM. The network is Gigabit Ethernet with public IPs, so we use dnsmasq instead of dhcpd to provide bootable images to our lab machines based on the clients' MAC identities. Student work (home directory) is backed up nightly and is available to them via ssh/sftp from off campus.
Verma Sameer (email@example.com)