Teaching methods go in and out of vogue. Old ideas fade; new ideas wash in like fads, fashions, and slang. Changes in the "how" often lead to changes in the "what." It wasn't too long ago that schools taught sentence diagramming. Today, who can diagram See Spot run?
Then there's technology, which drags curriculum in its wake like a runaway puppy dragging its leash. Perhaps that's why the Palmer Method is little more than a nostalgic memory today.
What's the Palmer Method, you ask?
My point exactly.
History puts on the pressure too. Compare what they teach in high schools now to what they taught in the 1850s or the 1920s or the 1960s, and you can only shake your head and say "Phew, the times, they sure have been a-changing!"
Pedagogy, technology, social change--all get reflected in What Kids Learn, or at least in What Schools Teach.
Have a look.