On a quiet afternoon somewhere in America, a couple of dozen employees gathered for an all-staff meeting.

Key points: Two Australians helped create an anti-gun violence video in the US

Two Australians helped create an anti-gun violence video in the US The video for March For Our Lives has been viewed more than 50 million times

The video for March For Our Lives has been viewed more than 50 million times There were 103 school shootings in the US in 2018

"Today, we're going to be learning what to do in the event of an active shooter," the boss said to the fidgeting group.

"We've brought in a special guest. She's an expert on this."

The expert was Kayleigh, an 11-year-old girl with blonde hair and blue overalls.

As she enters the room, the employees smiled, thinking it's a joke.

But they traded those expressions for gasps as Kayleigh offered detailed instructions in a calm, authoritative tone.

"If there was an active shooter, you would all be dead," she said.

"When you talk out loud, the shooter can hear where you are and where you're hiding."

Kayleigh continued to outline tips for dealing with an armed attacker — things like pushing chairs against the doors, what to listen for to detect the shooter's location, breaking and climbing out broken windows.

A few of her shocked adult students were moved to tears.

Some look away in discomfort. All were silent.

Kayleigh finished with a rhyme she learnt from her elementary school teacher, singing softly:

"Lockdown, lockdown, let's all hide. Lock the doors and stay inside."

The message: this is what American children learn at school.

It is all part of a video created by two Australians, Alex Little and Karsten Jurkschat, for March For Our Lives.

Australian creative duo Alex Little and Karsten Jurkschat (right) produced the Generation Lockdown video. ( Supplied: Katie Henry )

The student-led organisation was established after the February 2018 shooting at Marjory Stoneman Douglas High School in Florida.

Since it went live about a month ago, the video has gone viral.

It has racked up more than 50 million views and caught the attention of politicians and celebrities at a time when Americans are becoming increasingly numb to school shootings.

The pro-gun control group Everytown for Gun Safety counted 103 school shootings in 2018.

Video gained viral popularity in the aftermath of shooting

One student was killed when two teenaged boys attacked their peers at the Highlands Ranch STEM School in Colorado. ( AP: David Zalubowski )

School shootings are so frequent in the US that Alex Little and Karsten Jurkschat knew their video could be released at any time and would become relevant.

Within days of the video's release, one student was killed and eight others were injured by a gunman in Colorado.

It was the second recent shooting in which a student 'hero' was killed tackling the shooter, serving to re-ignite debate over who should be taking responsibility.

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That may be one reason why the video went viral.

It was only released on social media, and has since spread organically, Mr Jurkschat said.

The hashtag launched with the campaign, #GenerationLockdown, was trending on Twitter soon after the shooting.

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Mr Little believes the video's success lies in its truthfulness.

"There wasn't a lot of gift-wrapping around this. It's what kids in America learn in school. And it's putting it in an interesting environment, which is an adult situation," he said.

"Usually these secrets — these lockdowns — are kept in the classroom. And parents hear snatches of what kids are learning in school, but they don't really hear details."

'What if a kid was running this thing?'

Alex and Karsten moved to New York from Australia to work in advertising. ( Twitter: ADMA )

The two Australians moved to New York from Melbourne about two years ago to work as creative directors for the McCann ad agency.

There, they have won awards for their work with America's Football league and UNICEF.

Their latest idea came not from a client, but their own experiences in the US.

"It's interesting when you come into a new country; you see everything with fresh eyes," Mr Little said.

"Kids go to school and they learn about their times tables and their maths and at the same time how to survive a guy with a gun."

Inspiration struck when they had their own emergency training drill at work and noticed how disengaged the staff were.

"We kind of said to ourselves, 'What if a kid was running this thing? What if a kid was up there telling us how to survive?'" Mr Jurkschat said.

Creating authentic reactions took a year of set-up

March For Our Lives organisers jumped at the powerful concept and pro bono offer from the two Australians.

From there, it took nearly a year to find the right filming location.

The men wanted the reactions in the video to be authentic — not the work of actors — so they needed a manager willing to spring a confronting surprise on employees.

Mr Jurkschat said more than 40 offices declined to participate, and some managers feared retaliation from pro-gun lobby groups.

Kayleigh was chosen for the campaign after her mother filmed her describing routine school shooter drills. ( Supplied: Alex Little and Karsten Jurkschat )

March For Our Lives helped connect the ad makers with Kayleigh, an average young American who had previously offered support to the students' campaign.

"She did this really quick audition in the middle of a supermarket where she remembered from her own class what a lockdown drill is about," Mr Little recalled.

Kayleigh's mother filmed it on her phone.

"Although there was no set-up, no hidden cameras, the words she was saying were so powerful. She was so nonchalant.

"She grew up, as many kids in America do, knowing things like you should stand on a toilet seat so they can't see your feet. Things like breaking windows and climbing out because the doors are locked."

American kids are no stranger to drills

American schools regularly hold active shooter training drills to prepare both teachers and students for an attack. ( Reuters: Eduardo Munoz )

Currently, 42 states have laws requiring safety drills in schools, according to the Education Commission.

An analysis by the Washington Post suggests more than 4.1 million US students participated in a lockdown drill last school year.

There are no federal guidelines for what should and shouldn't be included in these exercises, but as more and more students die in school shootings, some schools are upping the intensity by using fake blood and firing blanks.

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In March, teachers in Indiana reported injuries and trauma after being shot "execution-style" with pellet guns during one such drill.

There's little data suggesting that lockdown drills work, and there's reason to believe they can have lasting psychological effects on students.

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For now, the creators of #GenerationLockdown are just trying to get the video in front of as many eyes as possible.

"I think each time that this is shared and seen, the less normal it feels for kids in America to have to learn this," Mr Jurkschat said.

"Our goal is to keep trying to shift that needle, to keep trying to get Americans, more people, more politicians to kind of realise that this is not a normal thing for kids to learn."