If you get into fielding or hitting position or a pitchers balance point with your heels on the ground you will most always have better balance. Try it rather than argue. All you have to do is lean forward slightly and move your weight forward over the balls of the feet. You will feel great balance on the balls of the feet with your heels still on the ground. Now try lifting your heels off the ground and only make ground contact with the balls of your feet. See which way has better easier more stable balance. You might want to start teaching it along with the other important stuff.