I don't know about disabling it, but you can filter.  There are a number of
products parents can use that are designed to filter objectionable sites
from children--among them is "Net Nanny," which is supposed to be pretty
good and easy to use.  PC Magazine had a comparison review of them several
months ago.  They all basically work by enabling you to put in keywords that
will, if accessed, lock out certain sites, newsgroups, etc.

You can also buy a locking keyboard cover, or unplug and hide both the
keyboard and the mouse after hours.  Really enterprising people would have
to bring their own--but I suppose it's being accessed by staff rather than
visitors?

Just suggestions.

Julia Moore
Indianapolis Art Center