We are looking for literature-based plays that are more serious or have a social message. Something along the lines of "The Hundred Dresses," which was a wonderful experience for us. Target audience is 3rd and 4th graders (maybe mature 2nd graders). We have looked at Hana's Suitcase already. Any ideas would be appreciated.

Thanks for the ideas. Some were new to me. I checked them out but not all were literature-based, which is one of our criteria. I liked Afternoon of the Elves and Number the Stars, but I'm still looking...

Jennifer,
Please can you expand a little more on the requirements:-
Firstly, the "audience" are kids.  What about the performing company?  Is this adults performing to kids or kids performing to their peers?
Secondly, what's your definition of Literature?  (Anything that previously existed in book form?  -  Aesop's fables?  Andersen/Grimm tales?  - or "high art" literature?)

Lazy Bee Scripts has various Shakespeare adaptations which could fit the bill.  There are a few Chekhov adaptiations, and Jane Austin's Pride and Prejudice - which would fit your performing company, but not - in my opinion - the target audience.  There's an adaptation of Frank Stockton's short story, The Lady or the Tiger, which I like, and possibly The Raven - though that is a "spin-off" from Poe's poem, rather than an adaptation (and it is certainly not a serious play!)