I used Topscore and achiever for practice tests. Sciences I only used kaplan and cliffs AP bio to study. Kaplan covered EVERYTHING needed for the sciences except for bio was lacking, but cliffs is so short It only took me 2 days to get through it the first time and 1 day for reviews. I wish I would have used CDAT for PAT. ps I had some questions from bio came straight off the topscore practice tests, I didnt even know that happens!!