You could do the three man drill as stated before, or for the younger team who may need the extra focus on their touch just send one player at a time, have balls sent into him/her from all angles (easily done by sending the rest of the team around the feild on the touch lines) and one by one have them knock balls into the boy or girl whos doing the drill. Dont have the whole team knock in the same kind of ball, maybe have one roll a ball in on the ground, have the next hit a bouncing ball, the next hit a chest high ball. Have two "goals"(two cones about 5 yards apart) set up with one cone on either touch line, so this forces the child to hit the ball to the wings. Have the Child start on at the penalty spot of his/her own goal, to show them the proper feild position when a clearance ball is appropriate. Reward well cleared balls (how ever you want, make it a compitition, or give them points, or offer less running or something) and put an emphasis on one touch clearances. You may as they progress toward the end of the year throw in a passive (just there to pretty much distract the defender, not to tackle the clearance) forward. Good Luck.