Sample of two.
My kid one took his very first SAT in spring of his junior year. I think it was the June date. Thank then took the test again the first fall date offered. In between he took a prep course and his score improved by several hundred points (I’m not making that up).
Kid two did the same test schedule and the same prep course…her score didn’t improve one point…not one.
But neither took the SAT the first semester of 11th grade.
I guess I’m trying to understand why your kid did this?