-home-
download ipig (ipig.iopus.com (i think)) and create a free account there, install it on a USB.
-in school-
plug in USB, run ipig (logging in with the free account).
that should work. don't forget to take the game with you too XD
-some hints/tips-
if used on vista, ipig needs to be run as an administrator
an ipig free account is limited to 10MB (about 6~8 hours of playing), then you have to create a new one
example: go to hotmail, make an ipig-account-series (i used ###

, where ### are 3 numbers.)
hope it helps