A 16-year-old boy who stabbed teacher Ann Maguire to death in a "monumental act of cowardice and evil" has been warned he may never be released from prison after a judge found his pride and lack of remorse in his actions "truly grotesque".

Mr Justice Coulson told Will Cornick, who stabbed Mrs ­Maguire seven times from behind as she taught a class at Corpus Christi Catholic College, Leeds, in April, that he must serve at least 20 years in custody before he is considered for release.

But he warned Cornick, who was 15 when he killed his Spanish teacher, that, having read about him, "it's quite possible that day may never come".

The court heard how the ­teenager held a deep hatred of Mrs Maguire, 61, and had planned her murder, telling many of his friends of his desire to kill her.

After the murder Cornick told experts he "couldn't give a s***", and added: "Everything I've done is fine and dandy."

In an attack that shocked the nation, the boy winked at another boy before he launched into a savage assault in front of a terrified class full of pupils.

Mrs Maguire was left with stab wounds including one that went straight through her neck and another that cut her jugular vein.

Despite this, the teacher managed to leave the classroom, pursued by Cornick, until a colleague bundled her into a room and held the door shut.

Leeds Crown Court heard Cornick then went back into the classroom, sat down and said "good times" in front of his traumatised classmates.

Teachers and police who detained him said Cornick displayed a calmness that ­continued as he was assessed by a range of experts. The court heard he has never shown any remorse and has spoken of his pride in what he has done.

When Cornick was sentenced yesterday he showed no emotion.

The boy had also talked of attacking other school staff, including a pregnant woman "so as to kill her unborn child".

Prosecutor Paul Greaney, QC, told the court there was ­nothing to indicate to the boy's parents or teachers a risk of ­homicidal violence. But he said pupils noticed disturbing aspects to his personality, with Cornick telling other children he hated Mrs ­Maguire and wanted her dead.

Two months before the murder, Cornick sent a message on Facebook that described Mrs Maguire as "The one absolute f****** bitch that deserves more than death, more than pain torture and more than anything that we can understand."

Cornick told a psychiatrist how he planned the murder.

Mr Greaney said Cornick told other pupils he was going to attack Mrs Maguire on the ­morning of the murder. The boy showed some of them the knives he had with him. Mr Greaney said Cornick left a room next to where Mrs Maguire was teaching and winked at a fellow student before going to attack her.

There was no expression on the boy's face as he stabbed her, one pupil said. The prosecutor said Cornick took a bottle of whisky to school to celebrate after the attack.

Mr Greaney said: "Undoubtedly, one of the most disturbing aspects of an extremely disturbing case is that (the boy) not only lacks remorse but is proud of what he did in killing Mrs Maguire, who he at one stage described to [a psychiatrist] as barely human."

Cornick told a psychiatrist: "I wasn't in shock, I was happy. I had a sense of pride. I still do."

Mr Greaney outlined psychiatric reports that had been prepared on the boy. He said: "In short, the defendant is currently highly dangerous and has psychopathic elements to his personality."