I have to say I don't care for the selective desaturation...the image is much more lovely without it.The light and moment you've caught are really nice as is the B&W conversion,so kudos to you on those points.
Wonderful shot of this little boy playing and the city in the backdrop. I have to say that the concept of cutting corners as a 'you're doing it wrong' example does not come off strongly for me because it competes with the overwhelming sense/observation of a little boy at play. Had you chosen an office setting with a guy in a suit doing something that captured 'cutting corners' as a bad thing that could get him fired that would have perhaps come off more strongly to match the spirit of the challenge. I feel that this picture would do far better in a Children or Playtime Challenge because that is this picture's strength.
At first, this seemed to be such an incredible reach. It had DNMC written all over it! DNMC DNMC DNMC!
But actually, I like it. I like the idea. And it works for me. I like the soft desat. That being said, his left hand ended up being very strangely dark grey (which isn't that big of a deal), and I think I would have liked a different angle. It's nicely done and processed, but as it is, I think it's a 6.