Certainly not a bad work, not at all.
With care in the details, there is barely any mistake that i can notice.
The poses are good and filled with movement. The size contrast of the characters also give it a nice touch to the image.
I'd say that the only things i can critique are maybe the simple gray background. And the fact that the shadow of the smaller character's left sleeve is missing.
In short: nice drawing, good attention to detail. There's a shadow missing but the rest is fine.