lots of schools censor myspace because kids often slander their teachers and other school administrators on that website.
if the video is so important, just send your teacher an e-mail with the link, and she or he can view it on their home computer.
you might want to search the other free video websites (metacafe, gootube, etc). there's so little original content on any of them... if there is a "good" video on the web, most likely there are several copies on all the various services.