No matter what you do, the teacher might not be able to see it, but the IT staff probably will. That is if you connect to the network. Plus, the webfilters are network based (or at least they were at my school, and at my place of work), so blocked sites would still be blocked no matter what operating system you're using or what browser you're using.
Wikipedia was blocked district wide from my school do to some n00bs vandalizing it at another school, but there was a way around it. IT knew, but didn't care. I used to go on there to edit and do administrative stuff all the time from school, despite Wikipedia being a blocked site.
