Issues with Proxy GPO on laptops for take home

So I work for a school district and we are having an issue with the GPO policy for our Barracuda Proxy. All of our desktops(2500 units) take the policy fine and block them from modifying the proxy but the problem is that the laptops are taken home so we are not able to apply the same policy because the staff would not be able to use the internet. In short we are trying to figure out how to get the GPO to only apply when they connect to the domain. The issue again is when they log in at home it uses a cached version of the login so the GPO is still applied. Any help?

I don't know if this is possible because I've never worked with barracuda but could you just port forward to the proxy server so their home traffic would go through it too?

Maybe I'm crazy but seems like that would at least work okay till you got a better solution

That is the key problem is we cannot trust them. They grown adults who act like children.

Could you just port forward the proxy server (again like i said never worked with Barracuda so I could very well be saying something about as useful as a screen door on a submarine. but it seems like that would work.)

The thing you want to do is not a proxy via GPO but the proxy auto discover stuff (via GPO). This is called WPAD 

http://www.experts-exchange.com/Software/Anti-Virus/Q_26247742.html

There's some things there you can google for a better answer (damn you experts exchange).

the WPAD will be found in office, proxy will be on. Out of office IE will stutter for a moment looking for the wpad file. It won't find it and life will continue without the proxy.