The husband of murdered teacher Ann Maguire has thanked an inquest jury, saying they have gone further than the police and council in investigating his wife's death.
But he added: "There is more to learn."
Don Maguire was speaking after a jury at Wakefield Coroner's Court concluded there had been safeguarding failings and "missed opportunities" in the run up to the attack on his wife by 15-year-old Will Cornick at Corpus Christi Catholic College, in Leeds, in April 2014.
The jury returned a conclusion of unlawful killing, but also noted as a contributory factor how none of the 10 students Cornick told what he was going to do to his Spanish teacher informed an adult before the tragedy.
Mr Maguire pushed for an inquest into his wife's death, arguing that no-one had ever looked properly at the facts surrounding her killing - especially why these children did not report what they were told that morning.
Speaking after the inquest, Mr Maguire said: "The jury has now started the process of learning lessons which should have been started three-and-a-half years ago.
"We want to thank the jury for their careful consideration of the evidence presented. The next step has to be to dig deeper and find out more."
He said: "They have gone where Leeds City Council, West Yorkshire Police, Leeds Safeguarding Children Board with its Learning Lessons review have failed to do so."
Mrs Maguire, 61, was stabbed seven times by Cornick on April 28, 2014, and died in hospital later.
After deliberating for more than a day, the jury of six women and five men said: "The 15-year-old pupil's intention to unlawfully kill a teacher was clear prior to the incident."
And the jury added: "Overall communication leading up to the incident was inadequate.
"There were missed opportunities to share and record problem behaviour."
It also said: "The safeguarding policy was not followed as no 'cause for concern' was recorded around the pupil's use of alcohol."
Coroner Kevin McLoughlin made a series of recommendations, including how he now wanted Facebook and other social media companies to introduce contracts to give parents responsibility for their children's messaging.
Mr McLoughlin also said he wanted a school policy of "see a knife, tell a teacher" to be rolled out nationally and that Ofsted should make safety around knives and other weapons a standard part of their inspections of schools.
He also said he wanted Amazon to investigate a suggestion that a second, smaller knife that Cornick had on him had been bought from the online retailer.
The coroner finally made a direct appeal to young people thinking of carrying a knife, asking them to consider Cornick's life sentence for murder and the 20 years minimum he is serving.
He said: "Carrying a knife could cost you your freedom and maybe your life."
Mr McLoughlin added: "You have to be exceedingly stupid to think it is a worthwhile endeavour."