Khan Academy is a very helpful resource. If I can't understand something in class, I always come to Khan Academy to understand a topic, whether it's precalculus or chemistry. Next year, I'll be taking AP English Language and Composition. This course is infamous for being very hard, no matter how well one did in prior English classes. It would be very helpful if an AP Lang course was added to Khan Academy. And, while you're at it, you could also add an AP Lit course too.