Instructions
Wait for Bullworth Academy to close after the sun sets. Find a window, break it and climb through to enter the school.
Walk up to any locker and look around to see if any guards are coming your way. If there are no guards, press "Triangle" to pick the locker's lock.
Open the locker to see its contents. If you see a Volcano 4000, touch it to add it to your inventory. Exit the school through the same window you came through before you get caught.