[ghaff]

So, beyond a fairly standard high school curriculum and not too much distaste for math, what implicit requirements should we add for physics, mechanical engineering, chemistry, chemical engineering, material science, etc.? Because where I went to school, there were no special requirements for those majors--nor for CS/EE. Is CS today unique for some reason among STEM majors?

Different majors have varying degrees of difficulty for different people. By and large schools don't (and shouldn't) get into the business of heavily policing who gets to give a particular major a whirl.