I started off showing them a bunch of different artworks from different time periods. We started with some photographs I found through google images (sorry for the lack of source info, I just googled "perspective photos" and I will post some links at the bottom of this).
|Raphael's "School of Athens", 1518|
|DaVinci's "Last Supper", circa 1495|
|Edvard Munch's "The Scream", 1893|
|Edward Hopper, "Gas", 1940|
|Edward Hopper, "Chair Car", 1965|
|Hard at work in the art room.|