We decided to use Debian after testing various distributions, but we really decided when a Debian developer showed us the real GNU/Linux. Thanks to firstname.lastname@example.org.
We use Debian Woody (kernel 2.4.18) to "hold" our link to Internet, using radio frequency, pcmcia modules and so on. We use IPTables and Squid to share the connection with the internal network. All in only one server. Other schools use the same solution. Live long and prosper, Debian.