A simple trick, and something of a once only event, the Pen Fifteen Club was used on every new kid at my school. Ask them if they want to join your club. Tell the new kid that all the cool kids are in the club. They will always want to join. At which time you take the industrial size permanent black marker and ask the victim to hold out their right hand. Then, very slowly, deliberately and neatly, write a huge PEN15. Because you did it on their right hand, the teacher will always see the PEN15. And the victim will not squeal.