Thomas Wyllie and Alex Bolland, both 15, were said to have “hero-worshipped” Dylan Klebold and Eric Harris, who opened fire on students at Columbine High School in Colorado in April 1999, killing 13 people and themselves.
It was one of the deadliest school shootings in US history.
Prosecutors told Leeds Crown Court how the youngsters who planned their own version of the attack in Northallerton were so serious about it that they had drawn up a “hit-list” of targets, including bullies and teachers.
They were just 14 when they were making their deadly plans, which included downloading bomb-making manuals and researching weapons.
Prosecutor Paul Greaney QC told the jury: “Eighteen years after the Columbine Massacre and nearly 4,500 miles away, two young teenagers in North Yorkshire became fascinated with Eric Harris and Dylan Klebold.
“The two teenagers researched and discussed those killers and their interest in them turned to hero-worship. It was against that background that they plotted their own attack upon the school they attended.”
Both warned friends of what they wanted to do, and Wyllie – who was described as the leader and main instigator – wrote about what jurors were told was his “twisted ideology” in a diary.
Among the notes in the journal – recovered from his home last October – were items he thought would be needed to go on the murderous rampage, including napalm, pipe bombs and firearms.
The inside cover featured a message apologising for either committing “one of the worst atrocities in British history” or killing himself.
In a secret hideout in Catterick Garrison, Wyllie also kept a rucksack filled with screws, boards and flammable liquid, which prosecutors suggested were gathered with the intention of building an explosive.
He was given the 12-year sentence, with his accomplice – who suffered from bullying at school and was said to have lost interest in the plan part of the way through – given 10 years.
In a message to a female friend last September, he revealed details about the plot.
She asked him if it was a joke, to which he replied: “No. No-one innocent will die. We promise.”
The following day, he made “clear and unvarnished confessions” to a teacher and then to police officers.
During an interview, he claimed that his targets were “infecting the gene pool” and that he and his accomplice would be doing a “service to society” if they carried out their attack.
The teacher present told the trial it was “the most dreadful thing that a student has ever said to me”.
“He was so emotionless about the plan,” the teacher added.
“He seemed to feel that it was something that needed to be done.”
The older boy, Wyllie, denied any knowledge of the plan during the interview, but the court heard how he started researching the Columbine massacre again within minutes of the officers leaving.
Jurors were told of how he tried to involve his then-girlfriend in the plan, describing her as “his Dylan Klebold” and repeatedly asking her to get hold of one of her father’s shotguns.
The boy – described in evidence by the girl’s mother as “devious and primitive” – also warned her that he wanted to murder her parents so that he could run away with her and become a “natural born killer”.
Her mother said he had “quite a lot of power and control” her, admitting she was “vulnerable” at the time.
The boy was eventually arrested after his hideout was discovered by officers on 22 October last year.
Three days later he was joined by the younger boy and his mother at a North Yorkshire Police station, with the force later accepting that they “did not meet those standards that are expected” in the way they dealt with the boys.
They both stood trial, but were found guilty of conspiracy to murder by a jury in May, with the older boy additionally being convicted of unlawful wounding.
The sentences were handed out on Friday, with the judge also lifting reporting restrictions on naming the teenagers after representations from the media.
Head of Counter Terrorism Policing North East, Detective Chief Superintendent Martin Snowden, said: “This is a deeply unsettling case and the cause of significant concern for all associated with it.
“The impact of it has been felt profoundly by the staff at the school, its pupils and their parents, and indeed the local community.
“We are extremely grateful for their support and the assistance we have received from North Yorkshire Police and the local authority during the course of our investigation.
“These boys demonstrated a very real interest in violence and had both expressed a desire to act out their fascinations.
“Disturbingly, they had gone beyond the fantasy and had begun to take very real steps towards making it a reality.
“They’d conducted research online, created a plan and identified potential targets.
“They’d looked into weapons, how they could get hold of them and where they could be stored.”