74 School Shootings Since Sandy Hook, As Obama Urges America To 'Do Some Soul Searching' (INFOGRAPHIC)

A staggering 74 school shootings have occurred in the United States since a gunman claimed 27 lives at Sandy Hook Elementary School in Newtown, Connecticut, 18 months ago.

The most recent occurred on Tuesday morning at a high school east of Portland, Oregon, where a gunman and a student are reported to have lost their lives.

That's more than one each week school was in session, with the longest gap between shootings spanning last summer's break, from mid-June to mid-August.

The figures were compiled by Everytown for Gun Safety, a group fighting to pass gun control laws.

The data comes as President Barack Obama made some of his most candid comments on the matter of gun control.

Speaking during a Q&A with Tumblr founder and CEO David Karp, Obama described it as his “biggest frustration so far” that America had been unwilling to take basic steps to end gun violence.

He said: “The country has to do some soul-searching on this. This is becoming the norm.

“Our levels of gun violence are off the charts. There’s no advanced developed country on earth that would put up with this.”

Children are escorted to safety during the shooting at Sandy Hook Elementary School

Obama insisted he respects the right to bear arms, but lamented the fact that even a modest bill to expand background checks on gun owners failed to pass the Senate last year.

The legislation fell victim to a GOP-led filibuster and pressure from the National Rifle Association (NRA).

Obama added: "Most members of Congress are terrified of the NRA.

“The only thing that is going to change is public opinion. If public opinion does not demand change in Congress, it will not change."

The Sandy Hook shooting saw 20 children and six adults killed on 14 December before gunman Adam Lanza turned the gun on himself.

Obama said the violence on that December morning amounted to the “worst day” of his presidency.

Lanza had earlier shot dead his mother Nancy. Police revealed the 20-year-old had an arsenal of weapons including guns, hundreds of rounds of ammunition, a bayonet and several swords in his home and car.

Investigators also found books on autism and Asperger's syndrome, as well as an NRA guide to pistol shooting.