<p>If you want to go to college in the US, you may want to take both the SAT and the ACT. Some students do better on one than the other. Note that the SAT is changing format soon, I believe in March 2016. So your current study materials will do you more good before that time. I think you can probably find more information on the upcoming change on the College Board website.</p>
<p>My kids took subject tests shortly after they finished the coursework related to the test. But I have to say, both generally had better scores in their junior year on the subject tests. They also studied specifically for the subject tests as well as doing their regular coursework. But they didn’t have APs in any subjects before taking subject tests (also none in their school until seniors). They did pick subjects they were strong in to start with (which may seem obvious 
).</p>