3rd grade organic stacked shapes

This is a lesson I've seen a few times on various art blogs and thought it would make for a great first lesson. It's a relatively easy lesson to teach and the results are great. The concepts I introduced included organic vs. geometric shapes, 2-D and 3D, and how artists create a 3D illusion on a 2D surface by adding shadows, contrast, and line designs (specifically using the 5 basic types of lines-horizontal, vertical, diagonal, zigzag, and curvy, as a springboard for them to create their own designs).

Here's a few finished examples: