Khan Academy could be a very helpful website if we could tweak a few things. First, once a person mastered a skill it should STAY mastered. I would suggest teaching the subject before you try to do it and take kids averages down. And DUMP AND DITCH Sal!!!!!! He has a lazy way of talking that is hard for kids to pay attention too him and his handwriting could use improvement. This was NOT intended to be mean review but SERIOUSLY MAN no one wants to listen to you talk for 10 hours!!!!!!!