The US has been rocked by more than 900 incidents involving gunfire on school grounds in the last 10 years, Joe Biden has said.
On Tuesday, Texas was hit by the deadliest school shooting for a decade when a teenager opened fire at a primary school, killing at least 21 people including 19 children.
Until the massacre at Colorado's Columbine High School in 1999, death tolls tended to be in the single digits.
Since then, the number of school shootings where 10 or more have been killed has mounted.
Here is a look at some of the worst to shake the nation over the past decades:
Robb Elementary School, 2022
At least 19 children and two teachers -Eva Mireles and Irma Garcia - were killed in a mass shooting at a primary school in Uvalde in Texas on Tuesday.
Four of the child victims have been named so far: 10-year-old Amerie Jo Garza, 10-year-old Makenna Lee Elrod, eight-year-old Uziyah Garcia and 1-year-old Xavier Javier Lopez.
The shooter has been named as 18-year-old Salvador Ramos. The rampage ended when he was killed, apparently shot dead by police.
He first shot his grandmother, who survived, before crashing his car near Robb Elementary School and launching the rampage.
It was the deadliest school shooting in a decade - and the second deadliest ever.
Santa Fe High School, 2018
Ten people were killed and 13 others injured in a massacre at Santa Fe High School in May 2018.
Among the dead were eight students and two teachers when a gunman opened fire at his high school in Houston, Texas after bursting into an art class.
The 17 year-old suspect, Dimitrios Pagourtzis, has been charged with 10 counts of capital murder and 13 of attempted murder.
A former pupil at the school, he has been found unfit to stand trial on a number of occasions and is currently ordered to stay in a mental hospital.
Marjory Stoneman Douglas High School, 2018
Three months before the Santa Fe killing, 14 students and three staff were killed at a school shooting in the small city of Parkland,Florida.
The gunman opened fire with a semi-automatic weapon in the hallway as students at Marjory Stoneman Douglas High School were going home for the day on 14 February.
Nikolas Cruz, now 23, has been charged with murder. He pleaded guilty last October and is now facing a trial to decide whether he is sentenced to death or life in prison without parole.
The shooter was a former student of the school who had been expelled the year before the massacre.
Umpqua Community College, 2015
A man killed nine people and wounded nine others at a school in Roseburg in Oregon in October, 2015.
British woman Kim Dietz, who was studying as a mature student alongside her teenage daughter, was among those killed.
Chris Harper-Mercer, 26, carried out the deadly attack before turning the gun on himself.
The killer is said to have asked victims to stand up and state their religious views before opening fire in a classroom.
Sandy Hook, 2012
Twenty children and six staff were killed when a gunman went on the rampage at a primary school in Connecticut in December 2012.
Gunman Adam Lanza, 19, killed his own mother in her bed at their home before going to nearby Sandy Hook Elementary School to carry out the massacre. He killed himself as first responders arrived at the school.
It remains the deadliest shooting at an elementary school in US history and renwed the argument over gun control.
Virginia Tech, 2007
A 23-year-old student killed 32 people on a university campus in Blacksburg , Virginia in April 2007.
More than two dozen others were wounded in what is still the deadliest school shooting in the US to date.
South Korean-born Seung-Hui Cho carried out the murders, before killing himself.
He initially shot two students in a hall of residence before going to the other end of the campus and killing 31 other people.
Red Lake High School, 2005
Five students, a teacher and security guard were killed at a mass shooting in Minnesota in March. 2005.
Jeff Weise, a 16-year-old student, also killed his grandfather and the man's companion at their home, before heading to nearby Red Lake High School.
Weise also killed himself after carrying out the slaughter, which at the time was the most deadly since Columbine.
Columbine High School, 1999
Two students killed 12 of their peers and one teacher at a school in Colorado in April 1999.
Teenagers Dylan Klebold and Eric Harris carried out the notorious massacre before killing themselves.
The pair had also planted a number homemade bombs at the school but they failed to go off.
At the time it was the deadliest of its kind the country had seen, and ‘Columbine’ became a byword for mass school shootings.
