Our school has it blocked but our techs block the sites in a way that you can't access it by typing
www.youtube.com, but you can access it through just typing in youtube.com . They realize their mistakes eventually, and our remote-firewall run by a company is very stringent, but as posted before, blocks websites that are used for school. Luckily i'm in web design at my school and because of a programming error our class is the only class that actually has more rights than a teacher has (Nothing major, but usually useful, such as unlimited logins which is great for robotics meetings so we don't have to wait for everyone to login, I just login on all of them when I get there).
P.S. I think the youtube.com spelling used to access it is made so that smart people who actually add the www can't use it, jk.