I am not sure Khan academy is a good way to judge what they know. My ds loves it and the way it introduces new topics that he does not know and videos on how to do them. May not be a great stand alone curriculum but really inspires him to learn new things and use his math. He is 8 too and elementary math can be very repetitive so there might be some test the school can give to see where she is. State sols for future grades is a good way for us.