Putting aside the fact that almost every teacher I have or have had in highschool with the exception of a few have been able to rip video clips off dvds, and the ones who couldn't would simply have student who was bright enough do it for them. Most schools/districts these days block youtube as well as facebook, myspace, etc, for reasons unknown as it seems to only serve the purpose of annoying teachers and students. Wonderful fun, our district also chooses to block many useful linux/programming sites as they could be used for hacking. SSH tunnels work for bypassing, but only if you're smart enough to get one set up.