So the second semester of junior year is about to start. While I have already taken the PSAT I don’t know if an existing practice ACT? Like one that multiple schools all take on one day? Also there are multiple test dates coming up for both the ACT and SAT. I just don’t know which one to take and when. Should I take one of them or both? Should I take them this year or senior year? Send help 
Here are the ACT and SAT websites for test dates.
http://www.act.org/content/act/en/products-and-services/the-act.html
Here are the major differences between the tests as I see them. Note that, as a math teacher, I’m MUCH more focused on the math than the other sections of the test.
SAT:
-Tests Math and Verbal; no science.
-Out of 1600 points, so small gains show up.
-Math section has 3 different types of questions: standard Mult choice, mult choice without a calculator, and fill in the blanks. Note that, of the 3, the standard mult choice tend to include the more difficult questions. But if you’re not strong on arithmetic, those calc-free questions may throw you off.
- Some of the questions aren’t the typical questions you’ll get in class. Some are designed to make you think! You may have to think outside the box for the more difficult questions.
ACT:
- Tests Math, Verbal and Science. Note that the science section is pretty generic; you don’t seem to need a strong background in Chem or Physics. Lots of reading comp and interpret the graph kinds of questions.
- Out of 36 points. So you’ll have to get a few more questions right to see any gain in score.
- All questions are straight mult choice, you can use a calculator for the whole math section.
- The questions tend to be more straightforward than the SAT. So a math question might ask you to find the slope, while the corresponding SAT question might ask you to identify the line with that slope.
Most colleges will take either exam, though you may want to check if you have a particular college you know you’re planning to trying for.
You might consider getting a review book on each test, and doing some practice exams. Prep for one exam won’t hurt you on the other, so it’s all time well spent.
Kids typically take the exam in about May of Junior year, and then again in late summer or early fall of Senior year. You’ll want those scores in so you can submit them with your applications in the fall.
So here’s what I would do:
Today I would go to amazon and order 2 review books, one for each test.
Between now and, say February, I would get a feel for both tests and try to determine which I preferred.
Schedule a May exam, then think about the August or October dates. Most schools will superscore-- they’ll take your highest Math SAT and combine it with your highest Verbal, even if the sections were taken from different test dates. So it’s to your advantage to take the test twice.
No college requires both the SAT and ACT for admissions so if you did well on the PSAT, then I would concentrate on that test only. @bjkmom gives great advice and I would try to get all your testing done by Fall Senior year so at you have a good list of target schools based on your scores and you can concentrate on other aspects of the applications.
For the California public schools, the Cal states will superscore while the UC’s will take the highest score from a single sitting. Having at least 2 test scores is advantageous for the super scoring. For other schools, you need to check the websites and see if they superscore. Also take the SAT and ACT with the essay since the UC’s do not consider any scores without the essay. Cal States do not require the essay and again other schools such as privates will have that information on their websites.
How did you do on the PSAT?