I just use an antibacterial foam which dissapates into thin air and leaves the keyboard supposedly clean from germs.
Got it from a company I use as my main computer supplier as they were doing a promotional on it at the time.
Another point of attack could be to have hand wash stations in the ICTsuites were the students can use an antibacterial gel as well as the staff and this would be more of a deterrent as it prevents the keyboards and mice from getting germs on them in the first place. Either way it will be expensive. :) ;)