The desired goal of high school math may not change much from year to year, but the best strategies for meeting that goal certainly do. I cannot imagine asking a student today to learn algebra the way I did 55+ years ago. Log-tables and slide rules? Probably not a good strategy.
Until one has taught something that is completely new to a student, it is difficult to imagine how challenging that can be, and how individual it is. What helps Johnny understand (or even care) is often completely different from what helps Mary. It is very difficult to teach effectively without figuring out what the student does not understand. And there are as many ways to misunderstand as there are students.
That is why teachers keep revising. They want to make the material more accessible to more of their students.
Until one has taught something that is completely new to a student, it is difficult to imagine how challenging that can be, and how individual it is. What helps Johnny understand (or even care) is often completely different from what helps Mary. It is very difficult to teach effectively without figuring out what the student does not understand. And there are as many ways to misunderstand as there are students.
That is why teachers keep revising. They want to make the material more accessible to more of their students.