A headteacher was found guilty today of failing to take reasonable care for the safety of his students after a pupil fell through a skylight.
John Summerfield, 64, took a group of "slightly inebriated" sixth-formers on to the roof of their school when Joel Murray, then 18, tumbled 8ft (2.4m) into a corridor and fractured his skull.
The teenager also broke his ribs, perforated an eardrum and suffered permanent damage to his eye in the fall at Sacred Heart Catholic College in Crosby, Merseyside, Liverpool Crown Court heard.
It took the jury of six men and six women less than two hours to reach its decision and Summerfield bowed his head as the guilty verdict was read out to the court.
The accident happened in August 2008 during an evening party the school had thrown to celebrate the students' A-level results which had been released that day.
Summerfield warned the students not to walk near the roof light, but the jury agreed with the prosecution that he should never have taken them there at all.
He was one of the only keyholders for a locked door which he opened to allow around 10 of his pupils through to gain access to the roof.
The prosecution argued that the locked door was an appropriate safety measure and, when that was opened, the principal no longer demonstrated "reasonable care".
Summerfield wanted to show them the results of some renovations to the building, and one witness told investigating officers he told her he wanted to give them "a once-in-a-lifetime experience" that they would be able to "talk about with their grandchildren".
During the proceedings, Kevin Donnelly, prosecuting, said: "Nobody was drunk but it is possible they were slightly affected by drink, possibly slightly inebriated.
"Mr Summerfield took a group into an area which was normally out of bounds. The decision was his and it was his alone.
"The very act of taking the students to that area was a breach of his duty of care. He failed to give appropriate consideration to the risks involved."
The barrister described the party as a "restrained affair" and said the students had consumed no more than "one or two" bottles of beer or glasses of wine.
Judge Gilmour QC told the panel: "This was a moment of folly."
He added: "He is a very caring teacher. He was doing what he thought would increase the enjoyment of the evening for some of the pupils and, in doing that, he didn't really think about the safety aspects of taking them on to the roof."