From Quora: My Answer to "What are some good prep materials and resources for the ACT and SAT?"

Try the Barron’s SAT Premium Study Guide, which is the 30th edition of Barron’s SAT. The 28th or 29th edition would also do. The ACT’s official study guide would work for ACT prep, as would the Manhattan Prep 5-lb Book of ACT Problems. You should also use the Khan Academy SAT prep materials SAT | Test prep | Khan Academy (they’re good, they’re free, and they’re the official SAT prep materials recommended by the College Board, the maker of the SAT), as well as the free SAT practice tests you can download from the College Board website. SAT Practice Tests
You can use my free YouTube channel for more help with SAT, ACT, and other standardized test prep: John Linneball Tutoring
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Hope this helps!