This is a group / teamwork activity I use with 3rd through 5th graders.

Objective: To enable students to work together as a group / team in order to achieve a specific goal

Materials: Hula hoops

Activity: "Hula Hoop":  Number students off and put them into groups with about 4 in each group. Have students get into a circle, stick both index fingers out, and place hula hoop on the back-side of their index fingers, with no other fingers touching the hoop and their palms facing downward.  Hands need to be about waist high. As a group, they must lower the hula hoop to the ground with no one losing contact with the hula hoop. All index fingers must stay in contact with the hula hoop at all times. The hoop will magically rise as if filled with helium (you might tell them that it's filled with helium at the beginning of the activity and then tell them the reason it rises at the end of the activity). It rises because they will most likely be unable to lower it all together so most of them will automatically raise their fingers thus raising the hoop.

Tangle of Hands: Have students get into two large groups. They must grab hands with someone else across from them, but cannot hold the same two hands of one person. It must be two different people. Without letting go, students must work as a team and untwist their hands until they are in a perfect circle. They may never let go of each other's hands.