Some of the courses in Khan are amazing, and others are hot piles of steaming garbage. Users need a direct way to rate courses so Khan other users know which courses to avoid until they are updated or fixed. Looking at you AP Computer Science, you hot steaming pile of garbage.
A 1~5 star system would be nice after you finish the course. It would also be nice to have something similar for each module within the course for Khan's use so they know which specific modules need updates, and which ones are getting great feedback.