Hi,
I am a senior in high school. Would taking subject tests in addition to having a decent SAT Score (1450+) help with college admissions for more competitive schools? Do certain scores on subject tests give credit for some schools? Are there any merit based scholarships given?
Look the website of each college you plan to apply to and see if any of them recommend/require subject tests. If they are recommended/required by some schools then you should take them, if not then IMO there is probably no need to take the exams.
SAT II scores do not get your college credit. They may be used for placement purposes at some schools (ex. my D’s college allowed a SAT II in a foreign language to be used in lieu of taking a placement exam).
If the colleges you want to apply to want SAT subject tests, then taking them and getting high scores can help (or avoid hurting by omission) for admission.
SAT subject tests may be used by some colleges for placement purposes (determining whether the student needs remedial math courses, or can get advanced placement in foreign language courses), but colleges often have their own placement tests for these purposes.
Check each college you are interested in to see if SAT subject tests may be useful.