Hello,
I took the Math 2 subject test in November with no preparation and scored 690. On the SAT 1 I got a 780 on the math section (2190 overall) so I’m wondering if I should retake the subject test. I’m a senior so January is my last chance to do so. Will improving my math 2 score help my application enough to justify retaking or should I stick with what I have? Thanks in advance for any insight you provide.
You should definitely try to retake it, with a lot of preparation. Math 2 is the exam with the highest rate of 800’s (an 800 is the 81st percentile, so roughly 19% of those taking the exam get the 800. That’s about 1 in 5 people getting an 800). A 690 in Math 2 is actually quite weak compared to a 690 in other SAT II’s, so retaking it to get a higher score will definitely help your application quite a lot, especially if you can at least get into the upper 700’s.
Good luck!
In January you’ll be done with apps so I think you may as well go for a higher score. Best of luck 
xxx
Even though your score is “low” depending on what you are aiming for, a 690 is not considered weak compared to other 690’s in different subjects just because of the percentile. Colleges don’t look at the percentile when it comes to evaluating a subject test score, they look at the score.