Bypassing NH2 Proxy Server

I am a teacher and our school goes through a proxy server. The school computers are set up so that they go directly to bess.proxy.mveca.org, port 7060. I have tried other ports and i have tried just taking it out of the internet connection prop. Some of our staff is able to bypass the filtering by entering their username and password. I am not sure how this script is working.

Thanks for your help,
Jeremy