A 14-year-old boy accused of shooting four people dead at a US high school and his father, who allegedly bought him the gun for Christmas, appeared in court on Friday to face murder charges.

Lawyers for Colt Gray, a freshman at Apalachee High School in Winder, Georgia, and his father Colin Gray, 54, declined to seek bond and they were ordered to remain in custody.

Judge Currie Mingledorff read out the charges and rights to the thin, dyed-blond-haired boy, who was dressed in a green shirt and khaki trousers, with shackles at the wrists and ankles.

Mingledorff told the boy he faces four charges of felony murder punishable by death, before later correcting himself and saying he would not be eligible for the death penalty because he is a juvenile. The maximum penalty is life in prison without parole.

Gray is charged with shooting dead two fellow students, also aged 14, and two teachers at his high school on Wednesday. Nine other people – most of them children – were wounded.

Gray's father appeared before the same judge shortly afterward, dressed in a black and white striped prison uniform and rocking back and forth nervously at the defendant's table.

He faces involuntary manslaughter and second-degree murder charges.

Earlier this year, the parents of another teenage school shooter were convicted of manslaughter charges, but Colin Gray is believed to be the first parent to be charged with murder over a shooting carried out by their child.

His lawyer also declined to seek bond and he will remain behind bars for the time being.

Relatives of some of the victims of Wednesday's shooting were in the public gallery during the two defendants' brief court appearances.

According to US media reports, the elder Gray bought the gun used in the shooting, an AR-15 style assault rifle, for his son as a gift last Christmas.

Georgia Bureau of Investigation director Chris Hosey said the father had "knowingly" allowed his troubled son to possess a weapon.

According to the FBI, the sheriff's office in Jackson County had interviewed the then 13-year-old boy and his father in May 2023, after receiving several anonymous tips about online threats to commit a school shooting.

"The father stated he had hunting guns in the house, but the subject did not have unsupervised access to them," the FBI said in a statement, and his son "denied making the threats online."

"At that time, there was no probable cause for arrest or to take any additional law enforcement action on the local, state, or federal levels," it said.

School shootings are a shockingly regular occurrence in the United States, where guns outnumber people and regulations on purchasing even powerful military-style rifles are lax.

Parental responsibility in mass shootings has come increasingly under the spotlight in recent months.

"How could you have an assault rifle, a weapon in a house, not locked up and knowing your kid knows where it is?" President Joe Biden said on Thursday. "You've got to hold parents accountable if they let their child have access to these guns."

In April, the parents of a teenager who killed four people in a Michigan school shooting were sentenced to 10 to 15 years in prison, in an unprecedented and closely watched case.

Jennifer and James Crumbley were the first parents of a school shooter convicted of involuntary manslaughter in the United States for the actions of their child.

Polls show a majority of voters favor stricter controls on the purchase of firearms, but the powerful National Rifle Association gun lobby is opposed to additional restrictions and lawmakers have repeatedly failed to act. (AFP)