The teenager's victim was found half-dead in a pool of blood and had to have large pieces of blood-soaked apple pulled from her mouth to stop her choking, Leicester Crown Court was told.
Mr Justice McCullough, detaining the boy under the Children and Young Persons Act, said no one could say when it would be safe for him to be freed. He said the situation would be reviewed in five years to establish whether the teenager, who cannot be named for legal reasons, could be released.
The judge told him: 'There is no mental illness or condition to account for what you did. Having tried to kill somebody once without warning, it remains possible that you may try again without warning.
'You've expressed no regrets or concern, but you did what you did. Your attitude before and after the trial has been to repeat that somebody else was responsible.
'If you will not tell people why you did it, you add to the difficulty of those trying to help you and then to avoid doing it again. No one can say now when it will be safe to release you.'
The boy denied attempted murder, attempting to strangle the girl and indecent assault in September last year. In July this year, he was convicted of all three charges after a jury heard how he lured the girl through a hedge and on to rough ground in Leicestershire.
He then tripped her from behind, strangled her until she lost consciousness and indecently assaulted her using either a part of his body or an object.
She was found in a pool of blood by her mother. Part of an apple had to be removed from her mouth by the emergency services so that she could breathe. The court was told the boy raised the alarm and called for help, claiming he had found his victim, but insisting that someone else was responsible for her injuries.
Anthony Smith QC, for the defence, said the boy had done a lot of 'early growing up' and might mature earlier rather than later, enabling him to be fit for an earlier release.Reuse content