Can WSUS Server update 2 seperate domains

I have a Windows Server Update Services (WSUS) Server that currently updates all our Admin PCs.
It is working really well and I want to use it to update our curriculum domain as well.
Is this possible and if so what do I need to do?
The domains are on different IP ranges and don't communicate between each other (although they do if you set up a host address in DNS)

I am thinking I can set up an unused network card in the WSUS server with a curriculum IP and then point clients to that through GPOs. Am i going the right way about this? Is this creating a security risk?

That is correct. As long as the clients can reach the IIS server running on the WSUS server then they can use it. There's no requirement for the WSUS server to be joined to the same domain as the clients for instance.

AFAIK, Windows Domains are irrelivant when talking about WSUS. As long as the client PC can resolve the IP address for the WSUS server and has HTTP access then it should work.

Your solution of an additional network card should work, or you could set up an old PC as a router, or just add another IP address to the existing card in the server (don't know if this would affect performance however).

I think dual homing is the easiest solution. Just make sure you educate IIS about the new interface.

I have two domains, I just put in a new nic and all worked fine. I use the server for Sophos deployment as well.

Not ran into any problems.

Update: It Worked!!!
I didn't even need to use the other network card.
All I did was set up a host in the curriculum DNS (this step wasn't even necessary - I could have just used the IP address of WSUS) and pointed to that in the Windows Update GPO.
IE7 was installed everywhere in a couple of days without me having to do a single local install!!!