"How useful is this in the professional world" is a pretty crappy metric for deciding what to teach, because the common set of useful topics is pretty small. We could easily stop public education at junior high or earlier if that's the goal. I've never, not once, needed anything from history class, or biology class, or social studies, or literature class in my professional life. Most people have probably never needed algebra, geometry, or trigonometry. But I'm pretty certain I would be worse off if school stopped at age 10, or if I just repeated the same stuff for 8 years after that.