SAT Subject Tests: Who should take them, when, and why?

What is a SAT Subject Test?
A SAT Subject Test is a one hour multiple choice test on a specific subject.
Collegeboard offers 20 different SAT subject tests, twelve of which are language tests.The most popular tests are Math I (Algebra and Geometry) and Math II (Trig and Pre-Calc), Bio, Chem, Physics, Literature and US History.
Each individual test is scored on a 200-800 scale. For a SAT Subject Score to be an asset when applying to a highly selective university, a score of a 650 or higher is necessary. In general, the lower the acceptance rate at the university, the higher the score must be to be considered competitive.
Who should take them?
Fewer universities require the subject tests than last year, but many still recommend or consider them. Most frequently 2 subject tests are submitted.
Only students applying to specific highly selective universities should take SAT subject tests. Here is the list of schools and their requirement level.
Also note that some universities will take an ACT test with writing, instead of both the SAT and the Subject Tests. Duke, Brown, Rice, and Tufts are a few that maintain this policy.
Students eligible for an SAT fee waiver are allowed to take up to six subject tests in up to two administrations free of charge. See the Guidance office at your high school to obtain the waiver.
When should I take them?
Any student, whether a freshman, sophomore, junior or senior, can take an SAT Subject Test. However, the best strategy is for the student to take the subject test when finishing the corresponding AP class. The AP exam is in May, and SAT Subject Tests are offered in June.
The SAT Subject Tests are offered on the same dates as the SAT test. Juniors and seniors completing their SAT testing must choose and either take a SAT or Subject Test(s). A student can take up to three subject tests on one test date.
World History and World Language tests are only available on specific dates.The language tests with listening are available only once a year.
Why should I take the SAT Subject Tests?
Students applying to highly selective universities where these tests are taken into consideration should take SAT Subject Tests in order to have the most competitive application possible. Solid scores on the appropriate tests can make a difference in an application and help a student be accepted to a university.