I suspect it depends on the age of the students. In grade school when kids are learning to read and do addition, it's hard to imagine anything more core than that and science/history taught at that age is more about getting kids exposed to those concepts rather than actual learning. But once kids get to secondary school and English transitions to British Lit, American Lit and other variations on "read books and write an essays", the actual class time seems much less important than science classes where high school students actually learn the core tenets of Bio, Chem and Physics.