Straight up assembly language, preferably Motorola MC680x0 or some other contemporary that was meant to be coded by hand; it's the only way, man! Plus students

Straight up assembly language, preferably Motorola MC680x0 or some other contemporary that was meant to be coded by hand; it's the only way, man! Plus students will gain some appreciation for how microprocessors actually work. In the same vein, just have them write code out on paper during exams and coding competitions like the way we did it back in my day. It's not as if they're not going to need that skill anyway when they get whiteboarded during interview loops when even the most lenient employers get exasperated at "CoPilot-only" graduates. </tongue-in-cheek>