I'm curious as to whether a concerted effort has been made to align Duolingo's lessons/assessments with Naitonal/State Educational Standards for Foreign/World Languages. (I'm sure that Duolingo currently meets a number of these standards, however unintentionally.)
Also, has Duolingo received word from any educators (elementary, secondary, or otherwise) who have successfully incorporated Duolingo into their classrooms? I would be very interested to learn more.
We're working on it, Jeffrey :).
So far, we've looked at how well people learning with Duolingo score on the WebCAPE test. We plan on doing more testing to figure out how your level on Duolingo corresponds to the score you'd get on different standardized tests. http://techcrunch.com/2013/01/17/study-learning-spanish-with-duolingo-can-be-more-effective-than-college-classes-or-rosetta-stone/
As for teachers using the site, a handful have told us through email or the forums that they are trying it with their classes. Our language team got to talk with a lot of language teachers at the ACTFL conference, and this year we plan on creating a dashboard teachers could use to follow the progress of students. We hope to work firsthand with more teachers soon to improve the Duolingo experience in schools.