Many teachers justify including Topic X and skill Y on a high school syllabus because colleges and universities expect students to have mastered topic X and skill Y for their courses. Not because Topic X is interesting or skill Y is necessary for success at the high school level, but because the next step expects it.
I wonder if the set of X and Y for high school teachers matches the set of X and Y for universities. I wonder how often university professors and high school teachers (and middle school or elementary teachers for that matter) get together to discuss this.
I wonder which of our assumptions about what the other thinks matches reality.