A SCHOOLBOY who attacked his former girlfriend with a kitchen knife after sending Facebook messages threatening to slash her wrists has been locked up for 32 months.

The 15-year-old attacked his 17-year-old victim at a Halloween night party while high on a cocktail of drugs and alcohol, Bradford Crown Court heard today.

The boy, who cannot be named because of his age, was led weeping to the cells to start a detention and training order after Judge Robert Bartfield told him it was "impossible" to avoid a custodial sentence.

The court heard the boy had taken Ecstasy, cocaine and alcohol after threatening the girl with the message: "I'll slit your wrists tomorrow."

He admitted harassing the girl on Facebook, wounding her with intent to cause grievous bodily harm and assaulting her friend, causing her actual bodily harm, when he recklessly cut her finger with the knife.

Prosecutor Charles Blatchford said the boy began a relationship with the 17-year-old girl after they attended school together in Bingley.

It was a turbulent relationship that ended early last summer when the girl was drinking and self-harming.

In October, the boy sent her a series of threatening messages, including "Both your wrists are getting slit" and "I'll do 25 years with a smile on my face."

The defendant, who wore a smart dark suit and tie, sobbed in the dock as the messages were read out in court.

Mr Blatchford said that on October 31, he and his former girlfriend both ended up at a party at a flat in Bingley.

At 3.30am, the boy threatened to punch her before picking up a kitchen knife and slashing open her left wrist.

She thought he was going to kill her and when her friend was injured by the knife when she intervened.

The girl was treated in hospital and said in her victim statement that she no longer wears short sleeved clothes in public because of the scar to her arm.

The boy answered "no comment" to all questions put to him by the police.

His solicitor advocate, Michael Reeves, said he was troubled and would be vulnerable in custody.

"This was a difficult relationship for both of them and he found it difficult to cope with," he said.

On one occasion, the girl had tried to kill herself by jumping into a canal.

She herself had said the wounding offence was out of character, Mr Reeves told the court.

Judge Bartfield said an adult would have faced a prison sentence of up to nine years and although the boy was able and intelligent, he was filled with too much self pity.

Sentencing him, Judge Bartfield said: "You sent her Facebook messages threatening to slash her wrists and leave her dying.

"Anybody would have assumed you were not serious, but you were.

"This was a very deep and unpleasant slash mark to her wrist that you deliberately inflicted upon her."