The tube of a cotton reel neatly accommodates a pencil. Loop a thick elastic band over the bobbin (fnuff!), pull back the rubber (phraa!), and you can fire the pencil out at puncturing speeds.
If the idea of launching a sharpened pencil into someone's face and eye causes you some concern, simply launch the entire school pencil supply into a polystyrene ceiling.
If anyone asks where you got a ladylike thing such as a cotton reel, answer "I stole it off a gay". If they ask why you are stealing things from gays, reply "to better know mine enemy".