Having to think two schools ahead (e.g. middle school math placement implications on college admissions) increases the dependency on having parents who know the system. Another example is the implications of taking college courses while in high school on law and medical school admissions.
Depends on the hs and the GC. And the college tier. Not all expect "most demanding. "
Less rigorous math in hs can affect a stem wannabe. If you really think everything else will line up for a highly selective, consider a summer course, see if the hs will then move up his math.
One of my nieces is applying to selective admit HS programs and one of the things that interests her isn’t necessarily a college-bound program. She asked me for advice, and I told her that whatever HS program she decides to attend, to be sure that she takes the courses that will meet requirements for her to be accepted at her state flagship college. She’s 13 now. When she applies to colleges in four years, she likely will have done a 180 about what she’d like to pursue. This will help ensure she has as many options open to her as possible when she graduates – to me, that’s the most important goal.
I didn’t take science junior or senior year or math senior year. (School was on double sessions and had a state waiver to offer only five classes. Instead I took AP USH and AP Lit as independent study, because our HS offered no APs.) I did pre-calc in college against the advice of my college counselor, who said journalism majors didn’t need math. (Ahem.) Did very well and now wish I had taken more.
S2 (non-STEM kid) took Calc AB junior year and no desire/need to take BC, and considered not taking math. The schools he applied to wanted a math class senior year, so he did AP Stat instead. Worked out fine, and is useful for a social science major. He was in a full IB program, so took honors physics and chem instead of the AP/IB versions to lighten the workload a bit. He took IB/AP Bio, which he liked.