The Florida high school where a former student shot and killed 17 people with an assault-type rifle is reopening for teachers on Friday as the community grappled with word that the armed officer on campus did nothing to stop the shooter.

That failure, plus reports of a delay in security camera footage scanned by responding police and several records indicating the 19-year-old suspect displayed behavioural troubles for years added to what the Florida House speaker described as an “abject breakdown at all levels.”

The Valentine’s Day shooting at Marjory Stoneman Douglas High School has reignited national debate over gun laws and school safety, including proposals by president Donald Trump and others to designate more people — including trained teachers — to carry arms on school grounds.

Gun-control advocates, meanwhile, have redoubled calls for bans or further restrictions on assault rifles.

Teachers were told they could return to the school on Friday to collect belongings from classrooms that have been off-limits since the slayings more than a week earlier.

The school plans an orientation on Sunday for teachers and students, and to restart classes on Wednesday.

Members of the Marjory Stoneman Douglas High School cross country team organised a run to honour their fallen coach, Scott Beigel, and the other victims of the school shooting. (Mike Stocker/AP)
Members of the Marjory Stoneman Douglas High School cross country team organised a run to honour their fallen coach, Scott Beigel, and the other victims of the school shooting. (Mike Stocker/AP)

“Our new normal has yet to be defined, but we want to get back to it,” said geography teacher Ernest Rospierski, whose classroom is on the third floor of the three-story building attacked on February 14.

Officials have said that building will be torn down.

Meanwhile, Mr Trump has said assault rifles should be kept out of the hands of anyone under 21 defying his loyal supporters in the National Rifle Association amid America’s public reckoning over gun violence.

He also pushed hard for arming security guards and many teachers in US schools.

“There’s nothing more important than protecting our children,” he said, adding that he’d spoken with many members of Congress and NRA officials and insisting they would go along with his plans in the wake of last week’s school shooting in Parkland, Florida.

But there were no words of support from the NRA for his minimum-age proposal — and outright opposition from organisations of teachers and school security guards for the idea of arming schools to deal with intruders.

“The NRA will back it and so will Congress,” Mr Trump contended as he called for raising the legal age of purchase for “all” guns from 18 to 21.

A spokesman later said Mr Trump was speaking specifically about semi-automatic weapons.

The president’s proposal came just hours after the NRA affirmed its opposition, calling such a restriction an infringement on gun owners’ rights.