"Writing Across the Curriculum" (WATC) has been an intermittently popular practice in the field of higher (and, I suppose, not-quite-so-high) education. As you might expect, WATC calls on teachers in all manner of subjects--not just English--to incorporate writing assignments. Some subjects lend themselves more readily to writing assignments than others. History, of course. Most of the other liberal arts--psychology, sociology, underwater basket weaving--also allow teachers to generate writing assignments without too much difficulty. Science classes require lab reports. When you get to subjects like math, though, things can get complicated. Not that students can't write about math--the very existence of math textbooks (unreadable though most are) suggests that mathematics can be a fruitful subject for writers to explore. But math teachers might protest--rightly, I think--that they have enough work to do just getting students to understand that a negative times a negative equals a positive (which I'm still not buying, by the way); expecting them also to help their students express themselves clearly in writing might be a bit much.
I thought of this today when I read an article in the Times discussing efforts to teach literacy and math skills in, of all places, gym. Gym teachers encourage students to count by fours as they work their way through a series of calisthenics! They incorporate vocabulary words into their inspirational exhortations! ("Yes, Johnny, that disk in your back is now herniated! Can you spell 'herniated'?") "Mother May I" provides ample teachable moments on the subject of Zeno's Paradox!
As a writing teacher, I would like to say to all those staunch advocates of WATC, "Thanks, but no thanks." I'm all for having students write as much as possible, but I don't expect non-English teachers to teach writing, any more than I would want to be held responsible for teaching math or--God help us all--gym! Believe me, if you need your kid to learn how to do a proper push-up, you do NOT want him to learn it from me.