[Technical] dynamic Internet browsing control

[Wayne Hewett]

Greetings
Does any school use dynamic internet browsing control applications?

It has been policy at Rosebud Secondary to allow students to have full
but filtered access to the web. 
We have the normal controls of IUAs, bans and real time account
monitoring, everything goes well. We operate on a student user pays
system once the free allocation has been exceeded. Internet cost is not
an issue since we are only a modest user.
There are times that I want some rooms or pods retstricted to the
internet - but still having access to the intranet. In a perfect world,
this could be teacher activated from an excutable from their laptop, or
scheduled well before. The IT help desk should be out of the loop in
terms of dynamically connecting or disconnecting the room.

There is a product called Browse Control out of the UK, but it is
expensive and only opeates at the IP level. I would like this to operate
at the MAC addreess level.

Any ideas?

TIA

Wayne Hewett
Rosebud Secondary College