When I was 14, a stupid prank involving cigarettes and deodorant cans in the boys’ locker room went badly awry, landing me and a pal in serious trouble for nearly burning down our high school.

After a laughably short suspension (it was the 1970s), the principal called us into his office for a talking-to.

Faced with our adolescent insolence, Mr McDermott struggled to find the right words that would shame us into contrition.

“You know,” he said, leaning in to deliver his coup de grace, “You’ll probably never be allowed to join the FBI after what you’ve done!”

The Federal Bureau of Investigation – variably seen as tireless crime fighters, chaste defenders of public order, sclerotic bureaucracy and an American Stasi – is both real and mythic, idealised or demonised depending on the country’s prevailing self-esteem.

It lurks, secret and vast, in the American psyche, embedded there by everything from America’s Most Wanted to Silence of the Lambs.

More than any other public institution it’s a Rohrshach test not only for our notions about crime, order and government power, but for our very ideas about right and wrong.

In the aftermath of another ghastly school shooting, news emerged that someone tipped off the FBI months ago that the alleged shooter Nikolas Cruz had posted a YouTube video saying he wanted to be a “professional school shooter.”

Students led away from the scene of the Florida High School shootings. Photo: Getty

FBI officials said they knew about the video but couldn’t find the young vlogger.

And even if they had, officials said, they would have had no power to order observation, start surveillance or even seize any weapons.

It wasn’t a good look. Critics on the right and left began to whisper about the bureau’s bungling.

It seemed a perfect opportunity for Donald Trump to scold the bureau for spending too much time on the “fake” Russian investigation and not enough time on psychotic teen gun nuts.

That Tweet hasn’t appeared – yet – but it would be in keeping with Trump’s ongoing battle with FBI brass.

Like a modern-day John Dillinger, he seems to be daring the bureau to bring him to justice.

Instead of a Tommy gun, his weapons are the memo and the innuendo, as he tries to steadily erode the bureau’s stature as an honest broker amidst Washington’s increasingly partisan battles.

Not a bad strategy, it could be argued.

To this long-haired kid in 1976, the FBI was a menacing presence, notorious for secret surveillance of the civil rights and anti-war movements of the 1960s.

For 48 years, the bureau was led by J. Edgar Hoover, a power-hungry tyrant who kept secret dossiers on presidents and even tried to have Martin Luther King Jr. assassinated.

But since then, the bureau has burnished its image more in line with the mob-fighting “G” Men of the 1920s and 30s.

It was a bureau assistant director, after all, who was Bob Woodward’s “Deep Throat” during Watergate.

After decades of Hoover, the bureau has been led by straight shooters like Robert Mueller, currently the special counsel leading the Trump Russia investigation, who served as FBI Director for 10 years under both a Republican and Democratic president.

His steadiness in the face of Trump’s taunting has been notable.

So while Trump tries to harken back to the bureau’s reputation as a secret police, the conspiracy theory isn’t getting much traction beyond the Fox News zealots.

Still, it’s ironic that those on the left who once reviled the FBI now defend its independence. An act of maturity or political expedience? Please.

But so far it’s the noble view of the FBI—as the last bastion of law and order in this increasingly vertiginous country—that’s holding out.

The Great Memo Crisis of a few weeks ago has faded, with both sides acknowledging nothing has changed.

But gaffes like the Florida shooting investigation, however unrelated and even unfair, will only encourage this president, who will not stop in trying to slip out from the law’s steady gaze.

Because it’s us, not the FBI, who are ultimately responsible for the bureau’s reputation.

And in a country where notions of right and wrong can’t seem to find proper footing, that’s a fragile thing.

Larry Hackett is the former editor in chief of People magazine in the US and a current contributor to the morning television news program Good Morning America. Based in New York, he writes regularly for The New Daily on American life and politics.