[Bagger Lance]

Another fun one to try is to line up two balls about 2 or 3 inches apart along the base of the plane line. Tee up the the ball in back slightly higher than the one in front. You can adjust ball position in a slight arc to accomodate swing path down the plane.

See if they can get both balls airborne.

Teaches and reinforces to hit down to get the ball airborne since the natural inclination is to scoop.
Also teaches "no quitting" since you must continue swinging through to get that second ball.