@manma11. I can give you what my own son’s progression was with standardized testing which may or may not give you a guide.
PSAT (Oct. grade 10: 1390 (660 ERW, 730 M) → timed Practice SAT at home September Junior Year 1530 (750 ERW, 780 M)
Timed Practice ACT at home (April of grade 9): 30C (33 E, 30 M, 29 R, 27 S) → Actual ACT September Junior Year 35 C (35 E, 34 M, 34 R, 36 S)
My son ended up never taking an official SAT because he was done after his initial ACT (He preferred the ACT as well). He spent most of the summer after 10th grade and early 11th grade preparing for the SAT spending 10-15 minutes a day on Khan Academy working on his weaknesses and took 4 practice tests (1480, 1480, 1500, and 1530). He took 2 practice ACTs (33 and 33 but with different results that superscored to a 35). He liked the ACT format better and being 1 and done by September of his junior year was a blessing with his heavy schedule. Good luck on reaching your standardized test scoring goals.