whitelist filtering software in windows xp embedded

[pins]

I hope one of you can offer me some advice: I know that there's one or two of you at least that work in education:
I want to find some decent, preferably free, software to filter webpages against a whitelist. It is to go onto NEC 'thin clients' that we are distributing to youths that are NEET (Not in Education, Employment or Training). We want to be able to make sure that they only access the websites that have their course materials on.
The machines run XP embedded, and have a limited amount of local storage space (though, apparently, hdd's are to be added to them).
I have done some googling, but not turned up a clear winner, yet, so any suggestions are much appreciated.
Cheers.

[nelz]

How about installing a transparent proxy server on the network and using that to limit the sites served? That would do what you want and reduce the bandwidth used by all these computers downloading the same pages and images.

[pins]

Sorry - I should have included to say that we are letting them take the machines home with them - and even providing them with 3g data cards!! Never had anything like that when I was at school! So it really has to be something that sits on the machine, that they can't tamper with.

[nelz]

I thought you said they were thin clients?

Could you configure the browser to force the use of your proxy server, or would they be able to override this?

[pins]

Yeah. Theoretically they are thin clients, but then it was decided that the load on our servers if 20 students were logged in and doing lessons, talking to each other and the teacher by VOIP would be too great, and so they should operate as stand alone systems as well. Great forward planning there, eh!?
I will have to look into your suggestion: they should not be able to override this as they will not have access to admin accounts on the machines. The problem may be (I am not actually responsible for this project, have just had it thrown at me as an after thought: "Tim, is there any way we can... blah blah blah?") that the lessons are delivered through a Virtual Learning Environment that is viewed in a browser window, in which case the load is still placed on our servers... what I have just thought, tho, and maybe you can knock this down if I'm being stupid, is that we could set up a DNS server on one of our machines, and configure the laptops/thin clients to use that DNS, which would only return results for the two or three sites that we would want them going to, any others would get a DNS lookup failed... Does that sound like it makes sense?
Thanks for batting ideas around with me, it helps a lot!

[ollie]

You can set the "thin/thick clients" to use a proxy on your server, even when "off-site". A proxy server running Squid and SquidGuard can handle thousands of clients at a time with no noticeable lag so 20 students would use very minimal resources. This doesn't have to be a large expensive box, a cheap PC is more than capable.

[pins]

It seems that RM are doing the proxy server for us, so that is good. Thanks for the responses and advice all.