2nd grade learned that size can show what is near and what is far away. They used this skill to create seascapes with near boats and faraway boats. My only stipulation was that each student had to draw at least one near boat, and at least one faraway boat, so some of the kids got really creative!
The next week, 2nd grade learned that overlapping can also show the viewer what is closer and what is farther away. They painted landscapes with overlapping trees for that assignment.
Since the students have completed both of these assignments, it has been really wonderful watching them use both of these concepts in other projects!