Students often are encouraged to think critically, to research thoroughly and, above all, not to believe everything they read on the internet.

Rebecca Fried, a 14-year-old rising ninth-grader at Sidwell Friends, a private school in Northwest Washington, took that approach to the next level when she challenged the scholarship of a retired professor and historian several decades her senior, getting her findings into the very same academic journal that published the professor’s work.

It started when Rebecca’s father, Michael, printed out an article by Richard Jensen, a retired history professor from the University of Illinois at Chicago, that he found online, according to the Daily Beast. The Fried family declined interview requests from The Washington Post.

In the 2002 article, published in the Journal of Social History, Jensen contended that Irish Americans have overblown the hardships they faced when they arrived on American shores, a belief encapsulated in reports of signs that read, “No Irish Need Apply.”

In an e-mail, Jensen said Rebecca misinterpreted her findings, characterizing the appearance of such ads as frequent when he maintains they were not.

(Photo credit: Ken Cedeno/Corbis) (© Ken Cedeno/Corbis)

According to Jensen, there’s scant historical record of those signs, and help-wanted ads in newspapers featuring the stinging phrase were “exceedingly rare.” He wrote in his scholarly article that he could find only about a dozen in the mid-1800s through the early 1900s.

He concluded that the claims of discrimination were an urban legend, a way for Irish Americans to claim victimhood when things weren’t that bad.

The “myth fostered among the Irish a misperception or gross exaggeration that other Americans were prejudiced against them,” Jensen wrote. This myth, Jensen argued, was perpetuated by drinking songs and lore.

Rebecca decided to investigate his assertions, searching an online newspaper archive for advertisements featuring the phrase “No Irish Need Apply.” She told the Daily Beast that she found many examples. As her research mounted, her father decided to reach out to Kerby Miller, a recently retired University of Missouri professor who specializes in the Irish diaspora.

Fried asked Miller whether his teenage daughter was on to something or whether they were being silly to challenge a widely cited historian, Miller said in an interview with The Post.

“No, this is incredible,” Miller recalled telling them. “This is terrific.”

Miller was at odds with Jensen when his paper was first published in 2002. The two traded barbs via e-mail lists, with Miller arguing that he had seen plenty of “No Irish Need Apply” advertisements. But neither he nor other historians ever formally challenged Jensen’s conclusions, which continued to be cited in other work. It was also the subject of an article on Vox.com, carrying the headline “ ‘No Irish Need Apply’: the fake sign at the heart of a real movement.” The article has since been revised to reflect Rebecca’s findings.

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Rebecca’s work culminated with an article in the Journal of Social History, the same journal that published Jensen’s work more than a decade ago. It includes a point-by-point rebuttal of many of his claims.

Rebecca includes dozens of advertisements that she found, and based on the frequency of them in newspaper archives, she concluded that they were, in fact, common. A reader of the Sun, a New York newspaper, would have encountered about 15 “No Irish Need Apply” employment ads in 1842, she wrote.

She found them across the country, from New York to Alpine, Tex., and in advertisements for a variety of jobs from hotel clerks to hog butchers. She sometimes found multiple “No Irish Need Apply” advertisements in the same newspaper, and the ads she found spanned from 1840 and into the early 20th century.

Rebecca took issue with Jensen’s other conclusions. Take, for example, his claim that “there is no record of an angry youth tossing a brick through the window that held such a sign.” Rebecca wrote in her article that an 1899 letter to the editor in Irish World and American Industrial Liberator recounted a mob of angry Irish Americans destroying a grocery store that posted that sign.

At the end of Rebecca’s article, Jensen was allowed to rebut the teenage scholar’s claims. Despite the evidence she gathered — he said there were 69 instances in 22 cities — he maintains that the advertisements were relatively rare: “I will suggest that that may be a lot for a historian to digest, but there was very little for an actual Irishman to see.”

But Miller says that Rebecca’s conclusions are important and hopes that it will put the question about the existence of “No Irish Need Apply” advertisements to rest.

“It’s not just important because she’s 14 years old and debunked a senior scholar,” Miller said. “It shows that the Irish in America were in fact victims of job discrimination.”