When working with cooperative groups, I keep the noise level under control by using colored circles. If a group is on task and using quiet voices, I give them a green circle. If I need to remind them about the noise level, I give them a yellow circle. If a group is way off task, I give them a red circle and step in to give them assistance. This is a great way to model appropriate behavior when I am just beginning to establish groups and ground rules. It also saves time because I don't have to interrupt the entire class to get one group back on track.