Hi,

I have been coaching for about 9 years and breast stroke is one of the hardest strokes to learn if you're not a natural. The timing for breast stroke is:

Pull

Breath

Kick

Glide

If he looks choppy, my guess is that he is missing his glide and taking another stroke before he is fully in streamline. Make sure he is stopping in streamline for a good amount of time to begin with. The easiest way is to have him count to 3 when he returns to streamline.

Make sure the timing is on cue. The kick should begin when your hands are together and finish the same time your hands extend forward.

This is the simplest way I can explain it for now. I hope this helps a little, even though this response if very late.