A 50-year-old male teacher has been taken to hospital after suffering stabs wounds at Dixons Kings Academy in Bradford.
His condition is described as stable.
Police who investigated the 1985 Bradford City fire knew who dropped the cigarette thought to have started the deadly blaze, a new documentary claims.
Retired Detective Inspector Raymond Falconer said officers worked out that an Australian man called Eric Bennett, who has since died, accidentally started the fire that killed 56 people.
A decision was taken at the time not to release his name, Mr Falconer told the BBC documentary - Missed Warnings: the Bradford City Fire.
Mr Falconer said: "He was obviously troubled. And I felt extremely sorry for him. And this would be weighing on his mind for the rest of his life."
The official inquiry into the tragedy on May 11 1985 concluded that it was an accident and was probably started by a spectator dropping a cigarette into rubbish that had accumulated under an old timber stand.
The documentary will be shown on BBC One in Yorkshire and Lincolnshire tonight at 22.45pm and on BBC Two nationally at 23:20pm tomorrow.
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Chris Dawkes at Valley Parade
The last time Bradford City were in the quarter finals of the FA Cup was in 1976 and the Valley Parade pitch was like a throwback to those times.
Needless to say the opening exchanges were scrappy with neither side able to put any meaningful passing moves together on the uneven surface.
The crowd at least were lively even though the football wasn't with City fans encouraged to bring their scarfs to the game to create a unique sea of claret and amber around 3 sides of the ground.
Both sides were guilty of committing a number of needless fouls which interrupted the flow of the game and it wasn't until 24th minute when Jamie Mackie's cross come shot was deflected into the arms of Ben Williams that either side remotely came close to opening the scoring.
However just 2 minutes later Mackie again burst free down the right. His cut back was controlled by Pavel Pobrebnyak, but the big Russian's shot rebounded off the post and bounced to safety.
10 minutes later it was Bradford's turn to scrape the paint off the woodwork - Gary Liddle's cross evading everyone but the post once again denying the opening goal.
It remained goalless until the referee signalled the end of the first 45 minutes. In a half with very few goalmouth incident posts at either end denied both Bradford and Reading the advantage in this quarter final.
CITY XI (vs Reading) Williams, Darby, McArdle, Davies, Meredith, Liddle, Morais, Knott, Clarke, Hanson, Stead
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