muck up day.....

Blow up the school. With everyone inside it. Hilarious for you, though less so for them.

ariight, heres the scenario....................
im currently in my last year of school and our muck-up (celebration) day is in 2 weeks time...........
i am usually very good at coming up with awesome practical jokes but at this point in time i am absolutly fukkin clueless as to what i can do.............

i need any ideas i can get...........
they need to be almost/just illegal and extremely memorable.....

any help would be greatly appreciated...
cheers.