This game is suitable for upper elementary school through high school. You can play it with any math topic. Prepare a sheet of problems of varying difficulty. Place a sheet on each desk in the room. Play music and let students work on the problems individually. Now stop the music and collect half the sheets. Turn the music on again, and let students work in pairs on the remaining sheets. When the time is right, turn off the music, and collect half the sheets again so that students work on the remaining problems in groups of four. Finally, play the music again and let students finish the assignment in groups of four. The teacher scores the exercise by counting the total correct answers on all the sheets collected through all the rounds so the group scores best when everyone works fast or when kids who can solve the hard problems focus on them. After your class tries this once or twice, they will figure out strategies to maximize the overall group score.
(This game was developed by Suzanne Lyons, founder CooperativeGames.com)