Students always take longer to meet your annual writing objectives than you think they will.
I’ve learned to set learning objectives for writing that I think students can meet by mid-course. If I’m wrong (I’ve never been right yet!), I still have plenty of time to do more teaching and/or to give students more practice.
Giving myself plenty of leeway to meet my writing objectives takes some of the pressure off me in teaching writing and off my students in developing writing skill. I don’t feel an obsession to mark more errors in the mistaken hope that students’ writing will improve in direct relationship to the amount of red ink I scrawl on their papers.
Also, if I can get a significant portion of the class up to competence even at the three-quarter mark, I can devote attention to those who need some additional help.