NaNoWriMo also offers awesome resources for teachers, and for getting your students writing!
I taught in a standards-driven school district, where test scores were king and no time in the curriculum calendar was allotted for creative writing.
Teachers in nearby districts, however, have some flexibility to teach creative writing, and most local high schools feature creative writing classes in senior and junior years. I spent time observing a fantastic middle school teacher, since retired, who had his students work on an annual scary story competition, and they wrote absolutely amazing stories!
He utilized a "writing workshop" setup, where students wrote, shared with peers, revised, "workshopped" their stories with him, rewrote again, and then copy edited. The emphasis was on plot development, and creating horror or suspense in the story. It was energizing to see students so engaged and truly excited about writing!
If you want to tackle novel writing, or even short story writing, with your students, I'd say check out NaNoWriMo's Resources for Educators. The resources are awesome, and sure to get your students writing.
The middle school workbook, downloadable for free, has many great writing exercises that could be used even if you're not writing a novel with your students! I love the "Good Book, Bad Book" exercises, the character worksheets, how to create conflict, outline your plot, setting and writing great dialogue, using comic thought bubbles.
They hit several ELA Common Core standards, including:
8.RL.2 - Determine a theme or central idea of a text and analyze its development over the course of the text, including its relationship to the characters, setting and plot; provide an objective summary of the text.
8.RL.3 - Analyze how particular lines of dialogue or incidents in a story or drama propel the action, reveal aspects of a character, or provoke a decision.