An essential skill for secondary English Language Arts is the practice of argumentation. Some writers view all modes of writing as arguments; thus, rhetorical skills are key to crafting persuasive messages for targeted audiences.
Writing is a process. It is recursive. No piece of writing is ever "final." Something can always be better. I often feel this way whenever I read back over my own old essays and inevitably find a sentence that could be better, a paragraph that could be stronger, or a word that could be more precise.
You may find yourself in agreement with Frost's famous quote when it comes to teaching poetry in the secondary classroom. However, love it or hate it, poetry can play a helpful role in teaching students how to write! Famous poems can serve as mentor texts for students and showcase key literary and rhetorical devices in action.