Here are two:
Blend My Learning (The Envision Experiment) - Oakland, California high school students who had failed algebra were randomly assigned to one of two summer school classes. The “control” classroom received a traditional five-week summer school curriculum for Algebra 1. The “treatment” classroom used Khan Academy for almost all of the period each day, and both classes had the same teacher. Take a look at their findings.
The Economist: Teaching Methods – An Alternative Vote… Using Science To Teach Science - This study involves the theory of “deliberate practice” by psychologist Anders Ericsson. This research team introduced a more interactive, discussion-based and assessment-oriented approach to physics class that strongly implies major improvements to science and engineering instruction in general. Read what they learned.