I agree with others who said strong math kids might run out of advanced math courses at SLACs without access to graduate courses at their own school or at a nearby university. My son rushed through and finished the undergraduate math requirements at his SLAC by the end of his second year, but luckily Wesleyan does offer graduate degrees in math so he could then work on courses and research towards a free 5th year Masters in Math.
My son also used Erica Meltzer for SAT Reading (3rd edition) plus College Panda for SAT Writing. I wrote out notecards on Quizlet for each book since especially Meltzer is extremely wordy and he wanted a short study program. He read my cards for each book section and then did the book exercises. He also did Khan Academy tests. I can message you the quizlet link to use if you decide to use these study books.