Joe Lister died when water suddenly rose in the Manchester Hole cave in the Yorkshire Dales on November 14, 2005, and he and 10 fellow pupils from Tadcaster Grammar School had to return through a passage known as the Crawl.
North Yorkshire County Council was yesterday found not guilty by a jury at Leeds Crown Court on two charges of failing to ensure the safety of the pupils and its own employees on the trip run from Bewerley Park Outdoor Centre, near Pateley Bridge.
Caving has since been suspended at the centre, which is owned and operated by the council, and after welcoming the verdicts the county's corporate director of children's and young people's services, Cynthia Welbourn, said it was too soon to make any decision about whether it would begin again.
The judge, Mr Justice Wilkie, said outdoor activity centres performed an invaluable educational function but there should be no complacency in ensuring safety.
The prosecution had been properly brought. "It has provided the opportunity for a full examination of what happened on the day and how the apparently unprecedented events of that day may have come about.
"I believe that some hitherto unanswered questions have been answered. I hope in that at least this trial will have been of benefit to Joe Lister's family."
Outside the court his family expressed disappointment at the verdicts.