@MITChris The two late afternoon classes at the UC are Special Topics in Math and Problem Solving type classes, and high school students who have taken them have said that the homework sets in past semesters required Linear Algebra. (However, the profs for these classes change, and there isn’t an official prerequisite, so who knows…)
As to what he wants to do, currently he’d want to spend more time on his astrophysics research and on 3D modeling. So, that’s what he’s doing this summer.
Regarding math, he wants one math class per semester, excluding summer. He wants “useful” math and found most of Calc BC to be “useful” and the first time he felt like he was in the right level of math for him. He prefers in-person classes over online classes. If he needs to do an online class to get the 1 class/semester, he prefers a class with lectures and a defined schedule over self-paced. There are still 3 waitlist spots for Discrete Math at the community college left. So, our fingers are crossed until July 13. Seems like Discrete Math would be pretty useful for some of the astrophysics research he’s doing currently.