A high school teacher's pledge to change the way he grades grammar is evidence of a dramatic shift in the English language

"Every student should do the best they can."

If you're a grammar purist, that sentence may have made you cringe.

Standard English dictates the word "they," a plural pronoun, should never be used to refer to a single person. Since "student" is a singular noun, you'd need a singular pronoun like "he" or "she" to match it.

A high school English teacher, however, wrote a convincing argument about why he'll no longer mark that usage as incorrect in his students' essays. His decision could be evidence of a dramatic shift in the English language.

In a column for PBS NewsHour, 38-year teaching veteran Steve Gardiner of Billings, Montana, said that forbidding the singular "they" has outlived its usefulness.

"I have burned up hundreds of red pens, and hours of time, correcting this grammatical usage based on a traditional gender binary of he and she. It's time to move on," Gardiner wrote.

"They" has gained considerable traction recently as a singular pronoun. The Washington Post added "they" to its style guide last year to accommodate "people who identify as neither male nor female." And in January, the American Dialect Society declared "they" its Word of the Year in a vote among linguists, grammarians, and lexicographers.

"It does say something about the way people are exploring gender and sexual identity, and perhaps a greater openness to accepting new ways of expressing that identity through language," Ben Zimmer, chair of the American Dialect Society's new words committee, told Business Insider in January. "It feels like an opening up of the language, allowing for a greater possibility of what these pronouns can refer to," he added.

By accepting the singular "they," Gardiner wrote, we can finally throw away the awkward constructions English speakers have invented to circumvent the issue.

Decades ago, masculine pronouns could be used to refer to someone of either sex, like in the sentence "The writer must address his reader's concerns." In the legendary writing guide "Elements of Style," E.B. White and William Strunk advised rewording that sentence to "As a writer, you must address your readers' concerns," according to the New Republic's John McWhorter. It's a compromise that sacrifices the conciseness of the original, though.

As society became more inclusive, English saw the advent of more workarounds, including the clunky "he/she" and the unpronounceable "s/he." And dozens of gender-neutral pronouns have been proposed over the years - including "heesh," "thon," and "zie," although none of them came close to catching on.

Meanwhile, the history of the singular "they" goes back centuries, as McWhorter pointed out in another piece. Shakespeare used the possessive form in his "Comedy of Errors," first performed in 1594:

"There's not a man I meet but doth salute me / As if I were their well-acquainted friend"

As the singular "they" creeps into the lexicons of writers and media figures, it's only a matter of time before it becomes fully accepted. Ultimately, Gardiner acknowledges the fight against the singular "they" is futile:

"Having fought this battle with students for more than three decades, I am ready to admit defeat. Every student is going to write what they want. Every broadcaster is going to say what they want. There, I even wrote it myself, and most readers probably did not notice."

Read Gardiner's column here.