Good works. The lines are looking very good. Although I agree with Ris that the lineweight can be varied a bit more, even with mechanical pencil. Lineweight is affected by both darkness and thickness afterall.
On the last post, the boy's arm is getting a bit too sausage-like. The muscle that's affecting the left side of the contour actually starts on the elbow, even though the bone would break it up just a bit. Good drawing otherwise though. I can feel the character.