This drawing exercise is one of my favorites. It uses a newspaper image as a starting point to practice shading. Even hesitant drawers can achieve pleasing results, having the edges of one part to begin drawing from and the other part as a reference. For best results, choose a fairly large picture with a good tonal range, clear but without excessive fine detail.

I've tested this drawing exercise on a group of 9 homeschooled children of various ages and drawing aptitudes, and they all enjoyed the activity. It really helped get them switched on to tonal drawing. Take care not to choose something too difficult, especially man-made objects in perspective, for hesitant drawers. The difficulty can also be reduced by removing a smaller section of the picture, although a fairly 50-50 split looks the most dramatic. This exercise is particularly useful for older children who are nervous about making the change to observational drawing, as the references give their drawing a crutch. Landscapes and figures are always great, or try a challenging smooth-toned automobile. Avoid very flat or cartoonish images. Have fun!
Go to the full explanation of the Newspaper Shading Exercise.