Here are some resources.

• My tutoring resources folder containing real SAT / ACT / PSAT tests and complementary book PDFs
• The College Panda SAT / ACT advice (dozens of good articles)
• SuperMemo Wiki on Learning (the best resource on learning I've seen)
• Cognito Mentoring Wiki
• Learning Wiki
• How to Remember Anything Forever (by Nicky Case)

Reading recommendations for high schoolers:

• Standard reading recommendations to improve your SAT / ACT verbal scores
• Everything on Wikipedia
• Paul Graham's essays: http://www.paulgraham.com/articles.html
• Brian Tomasik's essays: https://briantomasik.com/writings/
• SPARC Book Recommendations. But really, just read anything!