Call me Ed.
When I taught freshman comp last fall, I made a point of throwing in a few mini-lessons on grammar, punctuation, and usage. I also encouraged my students to invest in style guides and bookmark the Purdue OWL site. But my feedback on their papers emphasized ideas and expression.
My purpose in that course--and even more the next semester, when I started teaching Intro to Creative Writing--was to free them up and get them writing. Far too many freshmen arrive believing "good" writing is error-free writing. Writer's block is virtually guaranteed by that approach to pedagogy.
Creative writing is the single academic discipline in which students are encouraged to write the way they think and talk, where vernacular is valued and non-standard grammars respected. Ken Macrorie said it better than I ever could in his article on Engfish.
The ones who fall in love with writing will, I think, come to appreciate the structure of their language, and to teach themselves the rules.