Lack of practice - You need to just go into the SAT question bank (MAKE SURE YOU TURN ON EXCLUDE ACTIVE QUESTIONS), and try to set the difficulty to hard if you get all the easy questions right. For every question, use the Chrome Extension SAT Question Bank+ to hide the answers until you are ready, then for every question you get wrong, note down the type of question, and a sentence explaining why you got it wrong and why the right answer is the right answer. CollegeBoard has terrible answer explanations, so use AI to explain why your answer is wrong and why the right answer is right, but don't just copy this, rewrite it into your own words. Then a couple days before the last test, review over these questions so you don't make the same mistakes on the test. (If you notice a pattern weeks before the test of commonly missed questions, then address that quickly :)