Many colleges require or recommend that applicants submit SAT Subject Test scores. You can take them at any point in high school, but it usually makes sense to coordinate Subject Tests with your high school curriculum. You may not yet know if you’ll need to take SAT Subject Tests, but you can still prepare for the possibility.
The best place to start when deciding which test or tests to take is your current course schedule. If you’re in any AP or IB classes right now that correspond with an SAT Subject Test, there’s a good chance that the curriculum for the course will overlap with the test content. Subject Tests are offered in two levels of math (Math 1 and Math 2), Physics, Chemistry, Biology, Literature, US History, World History, and several foreign languages. If your school doesn’t offer AP or IB courses, or if you’re taking an honors or advanced level course that you think could be good preparation for a Subject Test, ask your teacher about it. S/he should be familiar with the test content and be able to tell you if the course you’re currently taking will prepare you.
Once you’ve decided on some options, take a practice exam in each subject. Your performance on the practice exams should give you a sense of which tests will be most appropriate. The College Board offers a detailed SAT Subject Test study guide that has several practice tests and provides detailed information on all of the tests.
Subject Tests are each one hour long and are multiple-choice (no fill-ins). They’re offered every time the SAT is offered, except March: October, November, December, January, May, and June. Many students like to take their Subject Tests to coincide with their AP exams in May or their final exams in June. Since you’re already studying for these exams, you can maximize your study time by taking Subject Tests around the same time.
You can take up to three Subject Tests on one test day, and as long as you’re registered for at least one, you can change your mind about which Subject Tests you’re taking (and how many) up until the day of the test. So if you’re unsure about the specifics of which Subject Tests you’re taking, it’s still advisable to register early and decide on the details as things become clearer on your end. Also note that you can take either Subject Tests or the SAT on a given test date, but not both.
As your College List firms up, you’ll have a better sense of whether Subject Tests are required. Though your list is likely still in progress, look at the standardized testing requirements as you’re researching colleges. If you notice that some likely contenders require or recommend them, you should plan to take them. If none of the schools require them, then you can hold off for now. Either way, pay close attention to the requirements of schools you’re researching so you are appropriately prepared come fall.