It is odd that the problem persists when parents try to give their children every advantage.
A few weeks ago, I received an e-mail from a US-based professor, whose Dean had reprimanded him for trying to teach his students how to write. "That is not a writing class," the professor was told.
The professor, who has been teaching business and law students at some of America's top universities for 50 years, told an MBA class that clear writing would be essential in their careers.
Each week in his class, they would compose a one-page memorandum, which he would read and mark (or grade). The memos would answer a simple question from their textbooks. "I wanted the assignment to be more about conveying their analyses than testing their ability to get the analyses right," he said.
Were they grateful? "The students complained so vigorously to the Dean that I was asked to stop." The students said that in today's business, they did not need to know how to write. "E-mails and tweets are the medium of exchange. So, they argued, the constant back-and-forth gives one an opportunity to correct misunderstandings caused by unclear thinking and writing."
The Dean insisted that the professor should make the writing exercise voluntary. By the end of the term, only one student, a non-native English speaker, was submitting the assignments.
The professor's worry about writing is widely shared. According to 2008 research, 46 per cent of first-year California State University students needed writing help.
The deficiency is not confined to undergraduates. A study published in 2009 in the journal Current Issues in Education found that a group of 97 US masters and doctoral students did no better in a diagnostic writing test than the typical college-bound high school senior.
Teachers at even the UK's top universities say the same. David Abulafia, a Cambridge history professor, said in a talk this year: "People do not know how to write. Command of grammar, punctuation and spelling is atrocious."
There was a need, Prof Abulafia said, to recover "an art (I shan't call it a skill) that has been lost and has to be instilled in first-year undergraduates even at Oxford and Cambridge: the ability to write continuous prose, clearly, elegantly, concisely, setting out an argument".
Is students' writing really worse, or are professors imagining a golden age of literacy that never existed?
People have been complaining about writing for a while. "If your children are attending college, the chances are that when they graduate they will be unable to write ordinary, expository English with any real degree of structure and lucidity," Newsweek Magazine said in a famous essay called "Why Johnny can't write". That was in 1975, and the experts blamed "the simplistic spoken style of television".
Today, Prof Abulafia says poor writing "may reflect a society in which fewer young people read and much of their informal writing consists of Twitter and Facebook messages". He does, however, also worry about rote learning in schools and that pupils receive no reward in examinations for having read more widely. He adds that many more students are now sitting school-leaver A-level examinations, which means teachers and examiners have less time to spend on each candidate.
Whether poor writing is new or old, it is odd that it persists at a time when parents are vying to provide their children with any possible advantage, exposing them to Paul Klee at the age of four, as the New York Times recently reported, and teaching them to sing "Heads, shoulders, knees and toes" in Mandarin.
If there is such a shortage of competent writers, why are ambitious parents not rushing to make sure their kids can compose an elegant English essay, and why are MBA students not scrambling to do the same?
One possible answer is that there really isn't much of a demand and that being a decent writer commands no premium in the job market. Are the US professor's students right in thinking that Twitter, Facebook and text messaging are all they need?
I doubt it. There are still jobs where good writing matters. It is hard to see those law students stepping up to the bench without being able to render a literate judgment. And I can't be the only customer who assumes that a banker who doesn't know where an apostrophe goes is going to be equally careless with my money.
There's a gap in the market and the smarter parents and students should get on to it. Good writing is far easier to master than Mandarin.