Such a cute image and a wonderful take to the challenge. I really like the composition and the pose just rocks. The main thing holding this back in my opinion is the patches of grass. Had those not been there the simplicity of this image would have been even more pronounced and would have boosted your score much higher, IMO. It seems trival but those little things end up meaning alot in these challenges.
Regardless, of your score this is a real winner. There is nothing about this that looks contrived, which is a great thing to capture! Good luck in the future.
I really like the boy's position (looking at his shadow but still walking) and the lighting is very good. I would have preferred to see the entire shadow but see how that could be hard to do.
Good choice of 'saying' and I like the way the little boy seems to be discovering his shadow for the first time. A little more contrast and sharpness would have given it more 'punch'