All the participants stand in a circle. The leader stands in the center of the circle and throws the ball to one of the participants. If the leader shouts 'catch' then the participant must head the ball and if the leader shouts 'head' the participant must catch the ball. If the game is just to fill time then if the participant gets it wrong they have to stand in the middle and be the leader. If the game is used to divide people up into groups then if the participant gets it wrong they will go out of the circle and into a group.