Ewww!! whay does my maltese puppy eat his poop?

And how do i get him to stop?? i bought the food my vet told me to, so he's not lacking any nutrients...and he is fed well, and let out on a regular basis... i try to stand at the door and wait till he poops, so i can get him away from it immediately, but i have 3 kids, so i can't ALWAYS wait... what to do???yucky yuck!!