There are several suggestions I will make, in spite of having no reference photo.
It is larger than life. This will cause trouble, especially on a children's portrait. Try to work just smaller than life. It appears that the individual features are out of proportion, possibly due to the size of your drawing. This can be corrected by better sizing of the drawing, and better line execution. Practice, practice, practice.
You have modeled the drawing well, but your line technique is weak. The lines lack expression and good execution. The point of your pencil needs more attention. The line work also is misplaced in some areas, especially on the viewer's right side of the face where it appears the light source is. The lines here detract, as well as the lines under the viewer's left eye and in some areas of the chin. They are too dark, and lack sensitivity. Try to make each line count.
Finally, try to place the portrait so that it does not run out of room, as it appears to have done at the neckline of the shirt. Think ahead!
Keep it up. There are no shortcuts!