A 13-year-old boy who showed “no remorse” for shooting his teacher and a classmate at a school in Indiana will be sent to a juvenile detention centre.

The boy admitted shooting Jason Seaman, a seventh-grade science teacher, and a 13-year-old classmate, Ella Whistler, during the attack at Noblesville West Middle School on 25 May.

He apologised for the attack during a hearing last week.

“I did not think it was sincere,” Hamilton County circuit judge Paul Felix said on Wednesday. ”No remorse was shown last week.”

Children seen evacuating Noblesville Middle School in Indiana following shooting

Judge Felix said evidence showed the boy planned the attack on his own and had intended for it to be deadly.

“You went into the school intending to kill not just two people but many people,” he told him. “You wanted devastation, an inescapable tragedy for the ages.”

The boy took two handguns and more than 100 rounds of ammunition from a safe in the basement of his family home, and brought them to school in a backpack, prosecutors said during last week’s hearing.

Prosecutors said the boy “is obsessed with violence” and made a video a day before the shooting in which he displayed the handguns and said: “Tomorrow’s Friday, you know what that means. I have to take other people’s lives before I take my own.”

Ella Whistler survived the school shooting at Noblesville West Middle School (Jenna Watson/The Indianapolis Star via AP)

Ella Whistler, the 13-year-old victim, survived despite being shot seven times.

The teacher, Mr Seaman, was shot three times. He testified last week that the boy returned to his classroom from the bathroom and opened fire.

Mr Seaman, a former football player at Southern Illinois University, said he threw a miniature basketball at the boy as he fired shots, and then tackled the youth and disarmed him.

Jason Seaman was shot three times before he tackled and disarmed the gun-wielding boy (Jenna Watson/The Indianapolis Star via AP)

The boy’s online history was filled with searches for school shootings, investigators testified, including “What was the largest mass shooting in America” the day before the shooting. He also searched for a “blueprint” of the Noblesville school.

Judge Felix rejected a request from the boy’s attorneys to send him to a private treatment facility.

He ordered the boy to the Department of Correction for placement in a state juvenile detention facility for rehabilitation until he is 18, followed by probation.