Here are some suggestions that may assist you. You don't have to try them all. Just pick a couple of them that work best for your child's needs.
1. Practice the SAT Reading and Writing section on
Khan Academy.
https://www.khanacademy.org/test-prep/sat-reading-and-writing
2. The College Board website has a
SAT Question Bank where you can study questions from the Reading and Writing section.
https://satsuitequestionbank.collegeboard.org/digital/results
3.
Bluebook SAT Prep Practice Tests
4.
Quizlet is great for studying SAT vocabulary words.
https://quizlet.com/57525022/sat-vocabulary-flash-cards/
Or you can purchase a box of SAT Prep Vocabulary flashcards.
5.
Linus is a great SAT Prep App is it similar to Duolingo
https://linusprep.com
Honestly, Khan Academy and the College Board SAT Question Bank were both beneficial to my child.