"Salman Khan spoke to Googlers in Mountain View, California on March 15, 2011 about Khan Academy: A World Class Education to Anyone, Anywhere.
Salman Khan is the founder and faculty of Khan Academy http://www.khanacademy.org/ a not-for-profit educational organization. With the stated mission 'of providing a high quality education to anyone, anywhere', the Academy supplies a free online collection of over 2,000 videos on mathematics, history, finance, physics, chemistry, astronomy, and economics."
Here is their Video Lesson on PE ratios.
I guess I am not sure on the grading, but it is a really cool concept...and in a way what we are doing in SIMM. For instance I do almost no lecturing in the class and people are at very different levelso sskill with the betetr people mentoring the others.