How to use UbuntuCE to augment our exisiting proxy

[chris308]

I have a unusual situation. Our school is sitting behind our district's content filter/proxy (BESS), but I need to further restrict and control our internet access. I would like to set up our own UbuntuCE proxy server to gain the additional control we need. On my home test LAN I can do this fairly easily, but can't seem to get things working at school because of our existing proxy.

I have tried setting Ubuntu to use a proxy in System>Preferences>Network Proxy I manually configured our district's proxy address, but no internet access results. If I unlock Firefox and set the district proxy address manually I gain internet access, but of course no filtering. :-(

I'm thinking there is a config file that I can modify to tell Dans Guardian to point to our district proxy instead of assuming a direct connection, but not sure about this.

Any assistance is greatly appreciated.

Thanks!
Chris