The evidence says that SAT prep courses do not make much of a difference: "From 1981 to 1990, three separate analyses of all the prior studies were published i

The evidence says that SAT prep courses do not make much of a difference: "From 1981 to 1990, three separate analyses of all the prior studies were published in peer-reviewed journals. They found a coaching effect of 9 to 25 points on the SAT Verbal and of 15 to 25 points on the SAT Math. In 2004, Derek Briggs, using the National Education Longitudinal Study of 1988, found effects of 3 to 20 points for the SAT Verbal and 10 to 28 points for the SAT Math. Donald Powers and Donald Rock, using a nationally representative sample of students who took the SAT after its revisions in the mid-1990s, found an average coaching effect of 6 to 12 points on the SAT Verbal and 13 to 18 points on the SAT Math. Many studies tell nearly identical stories. On average, coaching raises scores by no more than a few dozen points, enough to sway college admissions in exceedingly few cases." (from https://www.aei.org/articles/abolish-the-sat-2 https://www.aei.org/articles/abolish-the-sat-2)