As we teach kids about trying to decide what’s real and what’s not, the issue of digital images raises the bar. It’s a LOT tougher nowadays to tell if images have been forged. The first link below is a short movie showing a few examples of images that have been altered. I think it’s a great place to start.
The second link below takes you to a spot on a page containing several links to other sites that show forged digital images. I’m sure a good search will show even more. But, it sure is fascinating!
http://pages.citebite.com/g2a0l9q6h7jdx - lots more