It would be really great if KA could add a "I'm Guessing" button to their "SAT Full Tests" taken on KA. This would be a button off to the side that was not in the line of questions, and couldn't be confused with an answer. You could answer the question "B", but then click the "I'm Guessing" button. KA could mark your answer right or wrong accordingly, but also know that you don't know how to do the problem, and than teach you how to do it when you are practicing the problems you got wrong.
After I took the tests I looked back at the problems I had guessed on, and I had answered many of the correctly. I still had no idea how to do them, but KA didn't know that. As a result, I didn't practice those problems, and didn't know how to do them. And I got them wrong on the next test.
If KA knew I guessed on 15 questions on the test, even if I got 5 of them correct, KA would still teach me how to do them, and give me practice problems similar to the ones I got wrong. My score would still be based on the ones I got correct, but I could also practice the ones I got wrong. It seems to me like the best of both worlds.