My Son is a 14-year-old Freshman that is taking Honors Algebra II and H. Geometry at the same time so he can take an AP class in his Senior Year. I think he also said he wanted to take the ACT or SAT in his sophomore year. My son seems good at algebra and Passed with an A- (93) what are some tips I should give him? What workbooks/textbooks can help him do well in Algebra II?
I would have your son ask his HS math teacher for supplemental materials if he needs them.
Even if he did not double up, he would reach calculus in 12th grade:
9th: geometry
10th: algebra 2
11th: precalculus
12th: calculus
Presumably, he likes math and is good at it to be taking both +1 (geometry) and +2 (algebra 2) math (versus the normal level of algebra 1 in 9th grade). If that is the case, just the normal paying attention in class, reading the books used in the class, doing the work, etc. should be fine.