My daughter just tools the SAT last Saturday. We bought her an SAT prep book but only opened it on Friday night. She said the test was easy while her boyfriend that took the test with her said it was hard.
Anyway my daughter is a junior and straight A student who takes all honor class including calculus. So taking honor math classes from Freshman helped with math portion of the SAT. Best advice is buying him and SAT study book.
Congratulations to your daughter for studying hard and doing good work.