The boys, aged just 14 when they put together the plan in 2017, were said to have had a “hit-list” of targets, including students who had bullied or wronged them, as well as teachers.
During a trial at Leeds Crown Court, prosecutors told how the pair had “hero-worshipped” Dylan Klebold and Eric Harris, the teenagers who took up arms and killed 13 people in 1999 at the Columbine High School in Colorado.
Jurors were told how the plans that the two put together went beyond the realms of fantasy, as they downloaded bomb-making manuals, looked into purchasing weapons and warned friends of what was to come.
The older of the two plotters discussed his motivations for the attack in a diary which laid out what was later described as his “twisted ideology”.
In it, he apologised for potentially committing “one of the worst atrocities in British history”.
The younger boy gave “clear and unvarnished confessions” of the plot to another friend, refuting suggestions that it was a joke and telling her: “No one innocent will die. We promise.”
In opening the case, prosecutor Paul Greaney QC said: “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.
“They intended a re-enactment of the Columbine High School Massacre although fortunately, in the result, they were stopped before their plans were put into action.”
The boys, now 15, were both convicted of conspiracy to murder by a jury at Leeds Crown Court in May, with the older of the pair also being found guilty of unlawful wounding.
Following the verdict, Mrs Justice Cheema-Grubb told jurors: “Nobody will be in any doubt as to the gravity of their conduct and the plans they have made.”