This small little thing is very effective and shoots at a BIG distance for its size.
About this creation
This the pistol with a bullet loaded. You place it on top of the part the is held back by the 3L beam. The amo varies from 2x1-2x4.
This is what it looks like when it is shot. You simply push that 3L beam with the pin to the side causing it to flick like a catapult.
While the engineering it took to make this is pretty impressive, smuggling it into school would probably just get you a visit to the superintendent and the guidance counselor and a hundred psychiatrists, seeing how paranoid school administrators are these days. You're better off learning how to shoot rubber bands by hand.