To setup this game form a large circle of chair with one less chair than the number of teenagers.

Have a leader start the game by explaining the rules.  Each person will hold their left hand out into the circle.  The person in the center of the circle runs along the edge of the circle and grabs somebody's hand at random, that person in turn grabs another hand forming a line of running teenagers.

The person who started the line is holding keys, and when they throw down the keys everyone must find a seat.  The person left without a seat starts the game again.  To make sure everyone gets a chance to be in the line have the people that have already been picked not hold out their hand.  This game gets a little wild so be sure to ask the teens to be careful running and grabbing hands.