People vary, a lot.
OK, I've done NaNoWriMo twice, now. Hit the 50,000 word target both times, with time to spare.
Back when I was at school, despite several O-level subjects being based on written essays in the exam, nobody seemed to bother with teaching the basic skills of writing a good enough essay in a half-hour. I still managed to take and pass the English Language exam a half-year early.
I shudder at some of the writing I see published. And I doubt that I write well enough to be regularly published. I am, I admit, somewhat old-fashioned in my style, but I could never hope to emulate that found in the work of Paarfi of Roundwood. I have written in the sonnet form, but I am no Shakespeare. And my limericks are singularly inoffensive to the virginal ear.
Little of this can I credit to the efforts of my teachers. I was reading at an early age, with a voracious enthusiasm. I drank down books with all the enthusiasm of an alcoholic in a distillery. And I even bought my own copy of Fowler: the current edition seems to completely lose the principles which guided his advice.
I mentioned NaNoWriMo. One of the things they do is run a Young Writers' programme.
http://www.nanowrimo.org/eng/ywp
I find it unimaginable that any of my schoolteachers would have even looked at that. And, in this modern tested and regulated world, is there even the time in school to do this?