I wish someone would test spaced repetition software for high schoolers or undergrads.
What makes you think they haven't? When I look through the cites in http://www.gwern.net/Spaced%20repetition the majority of stuff was done with students of various age levels between elementary & college.
Spaced repetition alone has probably been floated around, but giving students tablets and making them use Anki themselves to study at home might be new.
Spaced repetition in instruction might work great as long as the single teacher running the experiment is doing it, and is then going to go away after the experiment stops. Some of the students exposed to Anki might keep using it by themselves after being taught to.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.