My two cents:
First, there are “core” versus “non-core” subjects, but some non-core subjects are academic, they just aren’t in the designated core areas, and instead are usually thought of as a type of “elective”. The basic idea of a core area is it just something which most people think every HS graduate should do up to a certain level (or perhaps covering certain topics, like US History in the US) as part of their “general education”. Colleges in the US often consider your general education to be continuing, so they may have certain things they are looking for in terms of preparation for their undergrad program when it comes to the core areas. Other academic subjects are considered non-necessary and hence “elective”, but of course many of those will be relevant to possible specific college minors and majors and such.
Second, when it comes to arts in general, there is a rough division between the academic study of arts (which can include theory, history, Art and X sort of topics, and so on), and the practical study of arts, where you are learning to actually do that sort of art. Of course the same one course could have some of both, but I think the typical assumption is many (not all) HS art classes are more practice-focused than academic-focused.
The same rough division persists in higher education, again with some courses, and minors and majors and so on, that overlap. But you can, say, get a degree in Art History, or end up doing a PhD in the Philosophy of Art, or so on, without actually studying to become an artist or performer. And there of course are professional artists, actors, musicians, and so on who don’t do much formal academic study of their art.
So to sum up, I think HS art classes are typically considered not core classes, and are also often considered more practical than academic (with some possible exceptions). But such classes may also be offered in colleges, and the HS versions may sometimes be valuable preparation for certain specific college minors and majors and such.