There’s no hard-and-fast rule, but the more time students spend on Khan Academy®, the more likely they are to feel well prepared for the SAT.
We recommend that students create their Khan Academy account in the fall of their junior year, if they don't have one already. Then, they'll have several months to prepare before taking the SAT in spring of junior year.
Help your students create a practice schedule on Official Digital SAT Prep on Khan Academy and stick to it. Like sports or music, the key to feeling prepared is committing to practice.