I don't know if this will work at your schools but I've found a way around our blocking system (Totally accidental and random) but go into Outlook and add the Web onto your taskbar - at our school we can get on all the blocked websites (for now...) then just start browsing the web.
There should be like a dark bar with an arrow - mine was on the right hand side of the toolbar, click on the downwards arrow then Add/Remove Buttons > Customize and check the box for 'Web'.