Why do you teach that, anyway? What's the point?
I get a variety of answers depending on the group. Sometimes I hear that the content in question is because that's what's always been taught in that grade level or course. I often hear that students will "need" that content for the next grade level/course, and that it's a good thing to expose them to it (What the heck does "expose" mean, anyway? Are we teaching by mentioning? Are we doing "just in case" teaching, just in case a teacher at an upper grade level requires them to know it?). Sometimes I even hear things like "because we decided it would be fun to teach it even if it isn't in the standards."
To me, those aren't valid reasons for teaching students anything.
The only good reason for teaching something is to help students learn the skill of transfer. Some content is chosen for us via state standards, and some is necessary background information so students have something with which to make connections to new knowledge. But the main end of teaching is for students to use that content in a meaningful way so they learn the skill of transfer, so the content doesn't remain isolated on an island of it's own, never to be connected or used again after the unit test, left alone to starve to death, forgotten. And it's a teacher's job to provide opportunities to practice transfer with carefully chosen content to get that job done, not memorizing a lot of informational bits they'll never ever use.
As Grant Wiggins stated, "The point of school is not to get good at school but to effectively parlay what we learned in school in other learning and in life."
Maybe I ask the wrong question when I get pulled into curriculum discussions. Next time I'll ask, "How will students learn the skill of transfer?"