All the places I have seen it it has been a dogs breakfast as just runs too slowly. I have no doubt that under a good network team who understand how to run a TC system and the kit required to make it work then it can work. However if it's a non specialist forcing governors etc to go down this route then make damn sure you have a water tight contract with your TC provider in place that you can throw back in their faces if the thing runs as slowly as I have seen in the past.

Personally I would not take the risk at this moment in time with the technology currently available, and with KS4 courses becoming more and more multimedia driven then that is a factor you should consider very carefullly. As pointed out by HH most video/graphics/audio software are going to struggle on any TC netowrk.

 We use thin clients here, for the reason mentioned earlier - easier admin of the network and they're cheaper overall.

 However, we do not use them in the areas where ICT as a subject are taught. The amount of servers at the back end required to do this would reduce the cost effectiveness to nill.

 Instead, they are used in a few clusters around the school for teachers to use with small groups of kids for researching, typing up, using things like Accelerated Reader or similar. We also use them in one of our 3 ICT suites, which is most used by English, History and other similarly wordy subjects. This allows the suite to handle anything that is thrown at them with ease. The most stress they get is the use of Flash games on websites, and they handle that easily.

 We also use them for our admin team, with SIMS.net and the like. Again, so long as they're set up properly and patched against the various glitches that can occur, they work well.

In total we have around 60 now and they run fine on a 2 server Citrix farm (although we actually run a 3 server farm, for extra expandability in the future, and for that extra bit of redundancy).

 Also note, those numbers are for 32bit Windows 2003 server. 64bit Windows 2008, or the soon to exist 64bit 2008 R2 will be able to handle things a lot better, as you can use an increased amount of RAM. Also remember, if you go down this route, fast disks are essential. If you can spec 15k rpm disks, your servers will thank you for it.

 So, the use of thin clients is a good idea, and a good use of budget in some locations in a school, but definitely not all! Careful planning, including a pilot are essential to get the most out of such a system, and to ensure people get what they expect from it. If you don't plan enough, you'll end up with a bunch of machines that you spec'ed up to be used for Office which a teacher wants to use Autodesk suite on...