You can't unblock anything on a school chromebook. So it's best to find website alternatives, things your school might use, like Giggl. It's a website with a built in web browser you can do almost anything, watch videos you can't on your school chromebook, netflix, hulu, vumoo, and even nasty sites... just don't go on those though. You can't play a lot of games and some sites are blocked as well. If you want people to send you videos that you can watch in a separate browser, i suggest using pad let. It is a app to post things like pictures or status' but people like me and my friends use it to talk to each other, you can send gifs, voice recordings, and take pictures. I hope this helps you.