I see a lesson here that's a mashup of social media literacy, close reading, critical thinking...but wait, that makes it Common Core-aligned, too!
My jumping off point was this brief lesson from Teaching with The Library of Congress. Learning to read captions and titles carefully can be a pretty powerful lesson in itself. The primary source examples used by the amazing folks at Teaching with the LOC would be perfect for social studies classes.
But why not expand the lesson? An easy way to do this would be to use newspaper headlines. Using www.newseum.org, have students look at headlines and captions from different newspapers on the same news story. Students can analyze headlines and captions, and compare how a news event is covered in different regions or countries. Have students write their own headlines and captions.
In a language arts class, have students write a newspaper front page using events and characters from a novel they've read. Adding images to illustrate their newspapers, either by researching primary sources or taking their own photos, and writing captions can help students recognize how captions can influence the reader's point of view.
(Images courtesy of The Library of Congress)