An idea for a school catapult project is to have teams of students build catapults with the goal of throwing a softball as far as possible. The team whose softball goes farthest wins a prize. Younger students create catapults for marshmallows instead.
For best results, the contest needs to include a rules list with specifications about the type of catapult device permissible, size limitations, trigger types and anything else of concern to the teacher. Instruction into the nature of catapults occurs before or during the contest.
Extensions of this basic project include requiring the students to collect and analyze data related to their catapult development, and give a presentation about what they learned at the end of the unit.