computer lab in a school enviroment

Sonicwall could be the best idea...

paralelly you can use TMG/ISA server as well

or you can use some third party proxy servers like http://www.squid-cache.org/
ccproxy etc.

I vote for Sonicwall. Relativley simple browser based configuration and provides all security servcies of a good firewall including all the features you request.  You could install it on the LAN, but its WAN ip address would need to be accessible to the outside world.

I tried the Untangle firewall, their demo site, and overall like the dashboard and reports that it has. Reports is something I wished SonicWALL baked in their OS. The Application control was gruesome on the Untangle. SonicWALL can block entire application by category in one click, here as the Untangle is application rules or by sorting through a list. The web filter on the Untangle is awesome! Wished that SonicWALL had the same feature. Overall I think the Untangle Is better suited for school, there are some setup differences and to me and I am biased, been using SonicWALL for years, but the SonicWALL seems more intuitive to me.  SonicWALL is a better choice for business my humble opinion of course.

Would gladly like to hear where you think the SonicWALL is lacking against the untangle (never heard of em).

View more example configurations and the SonicWALL webui and features on http://livedemo.sonicwall.com or http://ngfw-demo.com

tjguy, you can use both.  Put untangle in a bridged config and use only the features you want.  Stick with the free version... or pay for the components you want to use.

@JSpoor

SonicWALL is lacking in the Content web filter area. Otherwise SonicWALL does everything else great. I use the SonicWALL here at work and it does a stellar job at protecting the network. Untangle is just easier to get going (web filter) and has schools in their sights. I don't want to spend time getting the SonicWALL to work when I can the same thing in Untangle in a few mouse clicks. I did see the demos on both firewalls, and I am partial to SonicWALL, but I will admit that the Untangle is easier and has a better web filter built in. The school is in another state and someone at the school will have to admin the firewall at some point. I need something that is easy to learn.  In the end, it needs to keep the school protected from possible litigation and kids safe from the dark side of the WWW.

see demo site http://demo.untangle.com go under apps and choose the web filter.

@Lee W,

Yes, I am putting the Untangle in bridge mode, going for the full setup u50 at school pricing.