We have a point system similar to the one above that jwmcrae listed.  This year we are focusing on discipleship and we changed our point system in to a Martial Arts "belt" system. Everyone starts as a white belt and they upgrade to different levels. We introduced some significant challenges such as learning the books of the bible, the beatitudes, the lord's prayer etc.  We make sure all the kids get an opportunity to level up and be successful, but it also allows for kids who are really keen to progress at a rate they are interested.  Our prizes are very simple, packages of gum, book marks if someone obtains their black belt then they get a movie pass. We have even had parents ask if they could participate this year. We are using the Martial Arts concept to help the kids understand being a disciple who is instructed by the Master.