Below are several responses I received from readers.

James B. Morris writes:

This is not a new problem. When I was in high school (in the late ’70s) I went through the honors program for four years straight. We never read a single Dickens book, no Melville, or Milton. None were required. We read only one Shakespeare play (Romeo+Juliet of course).Instead we were pummeled with insipid and self-absorbed junk like Rabbit Run and Catcher in the Rye.
My cousin still brags that he made it all the way through twelve years of schooling and two years of community college without ever having to read a single book cover-to-cover.
We may be alarmed by today’s kids, and rightly so. They never had to hand-write anything, so their penmanship is hideous. Most can’t even hold a pen correctly between their thumb, fore-finger and middle-finger. Nowadays, they can type and text at blistering speeds. In the past , the length of time it took to draft an essay by hand allowed more cohesive thought. Teachers are not demanding, because their teachers were not demanding on them a generation ago.
As Prof. Alan Bloom traced in his brilliantly observant book The Closing of the American Mind, this is a 50-year-long problem that has just gotten progressively worse. It began in the universities. The students they taught became the teachers of yesterday, and their students became the teachers of today. Anyone who has watched the educational establishment since 1965 cannot name a single instance when universities increased the standards by which their potential graduates would be judged.
Our children’s poor writing skills is a direct result of those corrosive standards. They learn scant grammar, math and history. It is a crystal clear reflection of why they live as they do, and why they vote as they do.

Robert Calgaro:

I have two children (boy-girl twins) who are freshman at a major midwestern university. My son, who performed creditably in high school but who is not scholar material, is absolutely appalled at the poor quality of writing coming from his peers. In fact, he has made himself indispensable to his dorm mates by proofing their papers to correct the most egregious errors. My daughter, who is the scholar type, reports the same. Interestingly, they both attribute the cause to texting, facebook, and video games. They also attribute their superior (relative to their peers) ability to write to their Catholic middle school experience, when their 6th, 7th, and 8th grade
English teacher spent a significant percentage of class time diagraming sentences

[Me:] Diagramming sentences! I wonder how many education schools insist that prospective English teachers learn how to diagram sentences and the importance of teaching their students how to do it? I’d wager that in nearly every ed school, if someone suggested that, he’d be hooted at as a backward-looking rube who doesn’t understand that we no longer use such mechanistic and creativity-suppressing tools as sentence diagramming any more.

Nick Curran:

What a timely topic on NRO! I am a 38-year-old manager of, primarily, men and women right out of college or just a few years removed from graduation. In my line of work, the ability to write clearly and succinctly is very important. As a rule, the young men and women whose work I review cannot write at all. The mistakes are atrocious: subject/verb agreement, possessive-pronoun usage (invariably they use “their” when they mean “his” or “its”), incomplete sentences, run-on sentences.
I have always wondered how it is that these seemingly intelligent people have absolutely no ability to express themselves in written English. I believe that you and your other readers have nailed it. No one is requiring these young people to write in high school or even at the university level, which is astounding. I would add that it is likely that most students are not required to read good writing either. Harry Potter might be entertaining (arguable) and Maya Angelou might be the politically correct fad du jour, but neither is a substitute for Shakespeare, Donne, Johnson, or Hardy. I would imagine that if English classes are not teaching grammar or writing, they are surely not requiring students to read the great works of the English language either. No writing and no reading makes for late nights correcting errors in standard grammar for me!
Our Founding Fathers, with their enviable skill with the written word, would be scandalized if they knew how bad the writing was among the general populace.