Nice explanation, zztzed....Well said...
I would only interject that if the school DOES inspect the packets for content as well as headers, and blocks accordingly....this technology (in my experience) would be a VERY high cost to their speed and reliability as it relates to their network performance. I would suspect that they are doing nothing more than blocking the commonly used ports.
This can be worked around by using a different P2P product that is somewhat not commonly used.
Perhaps, Direct Connect might work??? or like you said using the good old tried and true methods like IRC and direct FTP channels, like in the days of old, might prove to be a good alternative.
I would say DO NOT be tempted to use the new ES5 (Earth Station 5) filesharing program....
Here is the link to the thread about that program....