I've taught this lesson for more than five years, as it's rich in art concepts, not to mention a great way to introduce 2nd graders to Vincent Van Gogh. Students learn about making forms out of shapes simply by adding the curved lines to their pumpkins. I also ask them to make their own orange (secondary color) paint by mixing red and yellow (primaries). The principle of space is touched on by using the simple concept of overlapping. Finally, they see how certain kinds of lines ("swirly" ones in this case) lend a feeling of movement to their skies - just like Van Gogh's in The Starry Night.