I get teaching parts of speech in elementary school; you are first learning to write, and need that to become a better writer, but what about middle school? In middle school, you already know how to write and read correctly, so why should we review those again? Plus, it’s just memorization, and when you get older, are you going to think “I just wrote a noun! Oh my goodness!”? No! Once you know how to write and read correctly (which should be before middle school) the parts of speech won’t serve much other use to you.