If you're in the US, public libraries often have test prep books to check out. They may be a couple years old but it should still be enough to help you and they usually have several practice exams in them. For free! A useful way to start studying is by first taking a full practice test as an assessment to see what topics and types of questions you struggle with the most, to help you structure and focus your studies. Also college board has a free sat question of the day that you can sign up for. Gives you a little practice even on days you're not studying and acts as a reminder.
~good luck~
hello! i found the khan academy SAT prep helpful in improving for the math section (mainly doing the practice questions and then reviewing what i was weak at) https://www.khanacademy.org/test-prep
there is also a free online, 1 month bootcamp (by founder of khan academy) with people who scored well on the SAT as tutors for Eng/Math sections
https://schoolhouse.world/sat-bootcamp
finally there are yt videos i would recommend like Anna's Universe
https://youtu.be/M2A0aOqVn3E?si=Oi0vcwqJnM2lL6AH
or Organic Chemistry Tutor (a classic)
https://youtu.be/yBCAv_NzzPQ?si=E0ln70lu4Ui1Bfim
finally the best resource you can use are the old SAT practice tests to time yourself and know how you would do. use the offical practice tests over others if you can
https://satsuite.collegeboard.org/practice/practice-tests/paper
this would probably be the best video to use from Anna's Universe if you had to watch one: https://youtu.be/KXF9u9iZRM8?si=UZal8zHuNBDAXjQc

this isn't really a manga related question but i need to study for my SATS upcoming in the summer, I was wondering if anyone had any good recommendations for studying or apps.. please, I want to secure a solid 1300 before my next one during senior year.