.... mandates , etc. etc. etc. gushing down from our imponderably oversized education bureaucracy ( and trying to comply with same) that he hasn't fully thought through his position on grammar.
Seems to me, teaching grammar is important. Ideally, teacher should be correcting grammar *all* the time, but it's quite possible he's not permitted to do so. ( See "crazy-ass directives", etc. above). Or he can only do it in ink of a particular color. Or only on stickies affixed to the paper, and not on the work itself. Or only if the corrections are phrased in a *positive*, not *negative* way.
When you let bureaucracy grow to the extent to which we've let ed bureaucracy grow, no question ( I repeat: *no* question) is simple.
So, short answer: teach proper grammar. It facilitates communication. This is .... inarguably... a net plus.
I'd be careful of dismissing all of those people on on Craigslist, however. We're a nation of English Language Learners. Most of us WERE and many of us ARE in that category. Failure to absorb the language instantly... in all of its complexity... doesn't imply lack of intelligence, motivation or any kind of moral failing.
Off topic but not really: does anyone know where/how/if the Common Core comes down on this question? ( i.e. teaching grammar.)
Speaking of "crazy-ass", and "oversized bureaucracy."