There’s a huge difference between studying a second language when you already have one under your belt than when you don’t. College German still flew by at a breathless pace, but having finally nailed French (by dint of spending a gap year there), all sorts of things fell in place that hadn’t at all with high school French. And luckily German is a language that few people have had in high school.
My younger son who took Arabic in college (he’d done Latin in high school) and found that nearly all his classmates had either had some Arabic or Hebrew and he floundered getting C’s his first two years. He did fine senior year after spending a junior year in Jordan.
I took physics without any physics in high school (pretty challenging ) and comp sci (but in a course designed for non-majors). I got a B’s in both. The real problem with the physics course was that it was full of premeds determined to get A’s!
I understand he wants to graduate with his class, but in the grand scheme of things I’m not sure it’s really the best plan.