Correct. The easy solution is to ban bittorrent and other P2P services.
not as easy as it sounds. those services are remarkably agile at dodging firewall rules
At home it's a bit easier. You can do stuff at the firewall but any parent should have their kid's computer's root password so they can get on whenever they need to. And last I checked there weren't any laws that prohibited parents from conducting random unannounced inspections of the kid(s) machines.