The family of a teacher murdered by a schoolboy have been given the go-ahead for a High Court challenge against a coroner's decision not to call other pupils as witnesses at an inquest into her death.
A judge in London ruled that Ann Maguire's husband, children and nephews had an "arguable" case which should be fully aired at a hearing in July.
Mrs Maguire, 61, was stabbed to death by a 15-year-old pupil as she taught a Spanish class at Corpus Christi Catholic College in Leeds in April 2014.
Will Cornick was later sentenced to life by a judge who ordered that he must serve at least 20 years, and warned that he may never be released.
An inquest into Mrs Maguire's death is due to take place before a jury at Wakefield Coroner's Court in November.
At a hearing at the High Court on Thursday, Mrs Justice Lang granted Mrs Maguire's family permission to challenge a "blanket" decision made by Assistant West Yorkshire Coroner Kevin McLoughlin not to hear evidence from students who had contact with Cornick "immediately prior to the murder".
She said the coroner decided "not to call as witnesses" those students who were aware prior to the murder that Cornick had a knife and planned to kill the teacher.
The coroner concluded the "risk of psychological harm outweighed the potential benefit", particularly given the length of time since the murder.
Mrs Justice Lang ruled: "In my judgment the claimants have raised arguable grounds for judicial review of this decision."
The family's barrister, Nick Armstrong, told the court it was the "only occasion on which a teacher has been killed by a pupil in a British classroom", and part of their case was that "it flows from this alone that all lesson learning that can be done, should be done".
It was the "first time something of this magnitude has happened, and it occurs against a background of increasing public concern about knives in schools, and a public debate about how best to respond to that".
Mr Armstrong told the judge: "All, including the assistant coroner, accept that student knowledge of school policies and rules on reporting weapons and behaviour is properly within the scope of this inquest.
"Understanding how this impacted on the absence of any report of Cornick's repeated intentions, and his possession of the knife, is obviously crucial to any lesson learning that may be done. Can the polices be improved? Can they be communicated better?"
The coroner, he argued, failed to take into account "material matters" when reaching an "unreasonable and irrational" decision.
He told the judge: "The assistant coroner made no inquiry as to the individual circumstances of any former student.
"None have been asked whether they would like to give evidence. No medical or similar evidence was sought. The assistant coroner gave no consideration to using any vulnerable witness safeguards."
Mrs Maguire's family said in a statement: "We are pleased with the High Court ruling today that the lawfulness of the Assistant Coroner Kevin McLoughlin's previous decision not to hear evidence from former students should be decided by the court in a judicial review.
"We hope this will be the first step on the road to establishing the true circumstances surrounding the murder of Ann Maguire."
Yogi Amin, a partner at law firm Irwin Mitchell, which represents the family, said: "The family have many unanswered questions and hoped that a full inquest, held in public, would examine the full chain of events and all the evidence available so that lessons could be learned to reduce the risk of similar incidents happening again.
"Ann Maguire's family have from the outset asked for a thorough, full and independent investigation into the horrific events that led to her murder by a pupil whilst she was teaching in the classroom. They believe this would be the best use of time and public resources.
"However they became very concerned about the scope of the full inquest hearing scheduled for later this year.
"The police investigation was itself limited in scope as the defendant quickly admitted responsibility meaning there was no examination of all the evidence publicly.
"The family want to know the full facts and hope that they will still be able to get the necessary answers through an independent and fair process at the Inquest."