does the sat percentile you get as a sophomore correlate with your junior sat percentile?

Does it stay the same?

Identical is very unlikely, but an earlier test score an a current score will likely fall in the same range. For example, National Merit is based on scores earned in junior and senior years. Factors such as levels of academic performance and motivation between sophomore year and now or may have some impact, but not enough probably to change the trend of scores dramatically.

It’s what we call “highly correlated”.

so if I got a 174, 55cr, 65m, 54w (I took the practice test they give you in the handbooklet so not much study) which was about 90ish percentile, If I study will my sat in junior year be at around 90th percentile so about 1900-2000? is it possible to gain that much? I have to take it in January before the format change.

I had a 185~ PSAT and a 2320 SAT so yes you can definitely improve.