This website really helped improve my scores is:
It has SAT WRITING, SAT MATH, and SAT READING. If you can understand all of the information or most of the info for the SAT MATH, I am pretty sure you will find scoring above a 600 on Math to be easier. There are tests after you finish a section to make sure you actually understood the information. I think this is better than Princeton (in my point of view). And, if you are taking the SAT on October the 6, I would split the 4 sections two a week leaving you with 1 week before the exam to do tests...I highly recommend you not taking any tests the day before the exam because some people get really nervous. That's just what I did.
I really hope this helps. I get most of the information from this website for the people I tutor and their scores have increased!!!
Sorry I took a long time to reply