The 17-year-old, who cannot be named for legal reasons, assaulted the victim in July 2021 and left her with numerous life-threatening injuries.
Following an investigation by the Kent and Essex Serious Crime Directorate, he admitted attempted murder and was sentenced at Maidstone Crown Court on Friday 4 March 2022.
He will serve a national tariff of 10 years and, should he be released from prison, he will be the subject of a whole life licence.
The victim of the case, a teenage girl, was found seriously injured in a field off Highsted Road, near the junction with Swanstree Avenue, by a dog walker at around 7.30am on Tuesday 22 July.
She is likely to have been laying seriously injured in the spot for at least seven hours.
Kent Police officers were immediately deployed to the scene and were joined by crews from South East Coast Ambulance Service and Kent Surrey Sussex Air Ambulance, who airlifted the victim to a London hospital.
At hospital, she was found to have 60 stab wounds across her body. A total of 99 injuries were recorded by a pathologist who reviewed the case.
Numerous people who knew the offender, and the victim, identified him as a possible suspect and officers detained him later that day.
A review of his phone led to detectives uncovering numerous deleted text messages which had been shared between the pair on the evening of the offence. Other messages saved on the phone showed he had a desire to stab the victim.
Immediately after the offence, he also carried out internet searches to try and learn how the police investigate murders.
A review of privately held CCTV, which was provided from numerous properties, captured the teenage boy walking to meet the victim late on 21 July.
Most of the footage showed a silhouetted figure walking in the distance but, from it, officers were able to track his movements to and from the scene.
They were also able to establish that the pair met at around 11pm on 21 July, with the girl last seen on camera at around 12.10am on 22 July.
With all the evidence in hand, Kent Police was granted authority to charge the offender the next day and he has been held on remand since.
Detective Chief Inspector Neil Kimber, the senior investigating officer for the case, said: ‘The brutality inflicted on the victim of this case was abhorrent and managing this investigation has been exceptionally harrowing. It is worrying that someone so young could have coldly calculated carrying out this sickening attack.
‘Throughout the course of our enquiries, providing the victim with the best possible support was our absolute priority. She has demonstrated exceptional bravery throughout and her fighting spirit is shown by the physical recovery she has made.
‘Despite being presented with a horrific case, the relentless professionalism of my officers meant we were able to unravel the crime, and detain the offender, within several hours.
‘The officers who first responded to the call for help also reacted with exemplary professionalism, despite being presented with a dire set of circumstances. Their actions ultimately led to the victim surviving this horrific attack.
‘I am pleased to see that this teenage boy has now been held to account. He presents a clear danger to the public and I sincerely hope that the support available to him in prison gets to the root cause of his dangerousness and prevents him from committing any further harm.’
