You could just allow blanket access, require everyone using a connection to get MAC address filtered access (so you know every device requesting access) and then log everything. Then provide stipulations that any live chat or forum use is forbidden. Anything except reputable / academic sources is forbidden.
To make it extra fun, tail the log of the access point live (projector?) and grep it through a few good regex to weed out junk and find any terms associated with IRC, forums, etc etc.
Allow them to ask for white listing sources, or provide your own (allow wikipedia, but not the discussions on each page which can be used to carry out conversations, etc).
Or just allow all net access but restrict access to just the sites you think are of use (wikipedia, specific journals, publisher's reference information, google for unit converting on the search bar, etc).