<p>Is it possible to study for the SAT and ACT at the same time? Does preparing for one test help the other? </p>
<p>It depends on what year are you at. It is definitely possible if you are at least months away from college applications. My D prepared for both test in the Summer after sophomore. You actually need a few practice to identify which test you would do better. If after a few practice and you are under time/budget constrain, then you may pick the one you perform better and focus on that one. In my state, ACT is mandatory while PSAT is a great opportunity that one should not overlook. So practically my D had to prep for both. After the practices over the summer, she reached plateaus in both tests with comparable scores. But still, she performed better in the ACT than the SAT in the real test, so she mainly used her ACT score for school application.
My suggest is, if you have time and budget allows, you should try both tests. The practice of either test will help the other test too as you are also reviewing general knowledge (not just test skills).</p>