Three “utterly cruel” schoolchildren who “lured” a 13-year-old boy to a park before stabbing him to death following a dispute on social media have been sentenced to custody in young offenders institutions.

Two boys, now aged 14, were said to harbour “grievances” with their former friend Olly Stephens, whom they had met only online, in the lead-up to his death at Bugs Bottom field in Emmer Green, Reading, on January 3 this year.

Olly, who had autism, had been coaxed to the field by a 14-year-old girl, allowing the two boys to “ambush” him with a knife.

His frantic parents raced to the scene, which was just moments from their home, after a witness raised the alarm, but he was already dead when they arrived.

The boys denied murder but were convicted during a trial at Reading Crown Court this summer.

The younger boy, who fatally stabbed Olly with a knife, was handed a life sentence with a minimum term of 13 years.

The older boy, who had fought with the victim in the attack, was given a life sentence with a minimum term of 12 years.

The girl, who admitted manslaughter and did not stand trial, was sentenced to three years and two months.

The court heard that she had made repeated revelations to friends that she was “setting Olly up”, even asking them to “pray for me”.

In another message, she wrote: “I don’t care if he f****** dies, I honestly don’t.”

As she walked to the scene of the attack, she told a friend: “Actually not even scared, I’m just like vibing, do you get me?”

The girl was visibly distressed during the hearing and was frequently seen to be wiping away tears.

Kate Lumsden QC, representing the girl, said she was deeply remorseful for her role in the killing, adding she has been suffering nightmares since the incident.

Sentencing at Reading Crown Court on Friday, Judge Heather Norton said: “What you did was utterly cruel and utterly pointless, you have taken one life and you have damaged your own futures and you have caused so much pain to so many people.

“No one can say how your lives and how Olly’s life may have turned out if you had not acted with such cruelty and such stupidity on January 3.

“The effects of what you did will stay with you, your families and with Olly’s family for ever.”

Olly’s parents, Stuart and Amanda Stephens, previously made an impassioned plea for young people not to use weapons following the guilty verdicts.

Children deserve a care-free and happy childhood, not to spend it cowering in their bedrooms, terrified and contemplating suicide because they are made to feel worthless by some random, spineless individual hiding behind a screen

They said: “So many young lives and the lives of their families have been devastated by this callous and cold-hearted act. Knife crime needs to stop. Now.”

They described their bike-enthusiast son as “a loving, caring, funny soul who would stick up for the underdog”.

Mrs Stephens added: “We’re broken. You know you’ve got to keep going and you do keep going, but the joy is gone.”

Mr Stephens called for mandatory “online ID” to be introduced, as well as a licence for the purchasing of knives.

Speaking outside of court, Mr Stephens said: “If it was up to me, no child under 16 would have a mobile phone

“Children deserve a care-free and happy childhood, not to spend it cowering in their bedrooms, terrified and contemplating suicide because they are made to feel worthless by some random, spineless individual hiding behind a screen.”

Detective Chief Inspector Andy Howard, who led the 200-strong Thames Valley Police investigation, said the case was “one of the most shocking” of his career.

He told the PA news agency: “I think the area that surrounds where Olly was killed, around his home address where all of these people – essentially central to the investigation – lived, that has particularly resonated and I think it’s something that will probably sit heavy on this community for quite a long time, sadly.”

Jurors were told Olly’s killers had shared several hostile messages about him on Snapchat in the days leading up to the stabbing.

The girl said in one message: “Karma – he (Olly) deserves all of this.”

The older boy said: “I actually hate the kid with a passion – if I was to see him right now I’d probably end up killing him.”

A woman who was at the scene said in a witness statement a number of punches were thrown, although the boys acknowledged that Olly was getting the better of the fight.

It was then that the younger boy stepped in and stabbed Olly.

Prosecutor Alison Morgan QC said the witness “could see blood coming from his chest and heard sucking sounds, which she knew was not a good sound”.

The court heard the boys “encouraged” others to search local news following the incident.

Ms Morgan said there “was no sign of any regret” on the part of the older boy, while the younger boy told a friend “it was the biggest mistake of my life” and that he carried out the attack “out of pure anger”.

She said at the sentencing hearing: “It was absolutely a carefully calculated ambush on Olly Stephens designed to ensure he was caught off guard with no idea of what was going to happen.”

The older boy, younger boy, and girl were further convicted of perverting the course of justice.

The offences involved the two boys disposing of their bloodied clothing and the girl deleting messages and apps from her phone.