At the Enosburg Schools we employed a filter last year, mostly for the
purpose of being a DHCP server.  It is called the SonicWall DMZ.  The
server equipment  costs $1,200 and the filter license cost $600/yr.  Plug
it in (about the size of a small hub) and configure it with a web browser
from anywhere.  I have an automatically downloaded list of approved
websites.  Approval is controlled by settings I make on a dozen different
categories and does not slow the connection.  I can block/allow sites
and/or IP# machines individually.  It has been proven very useful and
reliable.  I have had very few complaints from teachers about
inaccessibility (less than 10 so far, and I simply allow that particular
site). Students were upset initially because I blocked webmail (yahoo,
hotmail, etc.), but I offer them free "Enosburg" mail accounts upon
signing acceptable use policies...they have gotten used to it.  Not once
has a student complained to me or a teacher that a website they require
for research is being blocked!   So, so far so good...but to recycle a
quote from a fellow IT professional "just because no one complained
doesn't mean the parachute is perfect".  Hope the info helps.

Happy Holidays
Rob Gervais
Technology Coordinator
Enosburg Schools