Most students take the SAT during the spring of their junior year of high school. Many students choose to take the SAT a second time in the fall of their senior year after becoming familiar with the test day experience.
The College Board has its shares of inconsistencies. On the one hand, they insist that preparing for the test should not increase one's score by more than 30 or 60 points (probably changed a bit since the days of the 1600 SAT) and that such increase might be accounted by "aging" a bit and be more familiar with the test. And yet, they do sell an online "prep" package and have "offered" it to residents of states such as Georgia and New York. Do we really believe they sold the "package" to the officials by saying ... "Look this ain't working too well, but you should buy it for the kids?"
However, back to the discussion of my recommendation --which is NOT based on taking the tests in 9th grade. What I have recommended is to start in the summer between the sophomore and junior year with the objective of sitting for the PSAT and SAT at the same time. The reason is that the PSAT might be important for certain students who have the potential to score high. Fwiw, some students might have started a slow preparation after receiving the scores of a practice PSAT taken in 10th grade. But again, the summer before the Junior year is ideal as one can devote more time than during school and should not have the pressure of the "last" summer before senior year.
The benefit should be to have the preparation bringing up the PSAT score as opposed to take it ... just to see what happens. After receiving the scores of the PSAT and SAT scores, one might continue the preparation for the January administration or even a later date. If all fails, there is always the summer before senior year and the October senior year session.
If I might repeat what I wrote before, the idea is to follow a slow and consistent approach as opposed to intense cram sessions. With the bonus of plenty of time and low pressures, one can see a consistent increase in comfort with the ways of TCB. A longer period of preparation also allows for checking the latest discussions on the test and keep the information fresh.
And, fwiw, this does not require taking 35 to 50 past tests and learning silly lists of 3500 words. We are talking about 2-3 sections a week, including some with open books and WITH the answers.
Again, there are no "best" approaches, as the testers are individuals with a wide range of prior preparation. I do, however, like what I advocate because it is extremely low cost, low pressure, and that it ... has worked rather well for more than a few students. And, if I am wrong, there is always Princeton Review to take a few thousand dollars from your wallet, and send a stressed out student to take the latest test possible.