Supplies needed: straws, q-tips
Students are split up into 2 teams. Give each student a straw, and split up q-tips evenly between the two sides. When you say go, students pick up the q-tips and blow them to the other side. After a pre-determined amount of time, say stop. The team with the fewest q-tips on its side wins. Or it can have no purpose other than an energy-waster.
Beware: don't let your teens tilt their heads back to far or the q-tip will go into their mouths.