Hi Steven, there is no authorized way of grading a student based on Khan Academy activity. If you did not have Khan Academy, I am guessing you would create a system based partially on how homework compliance, partially on activity you see in class, and partially on performance on tests. With paper based homework you'd be on the lookout for glaring evidence of plagiarism, but sometime that is not so evident - nor do you know how much homework help a child has had from a parent. That is why the work you can actually observe in class and during tests matters a great deal.

That, I think, is no different when using Khan Academy.

A couple of other teachers discussed it here a while ago: https://khanacademy.zendesk.com/hc/en-us/community/posts/205000978-Grading

After the new updates they may have other things to add. Obviously, with new mastery criteria and more exercises in a mission, how a score is perceived may change. I am moving your message to a more appropriate part of the forum for your question.