The first charge against the OPC was that, as an employer, it failed to take all practicable steps to ensure the safety of employee Jodie Sullivan, while at work.
Ms Sullivan was the instructor in charge of the group when they were swept to their deaths in the Mangatepopo Gorge, near Turangi in the central North Island, on April 15 last year.
The second charge was the centre failed to take all practicable steps to ensure no action or inaction of Ms Sullivan harmed any other person.
The students and their teacher were on a canyon trip when heavy rain dramatically raised the levels of the usually sedate stream.
Department of Labour lawyer Michael Hargreaves said the OPC should have known from the heavy rain on the day that the group should never have entered the gorge, even though the water levels were not high when they entered.
The OPC should also have either subscribed to Met Service's weather warning service, or kept an eye on its website for weather warnings on the day of the tragedy.
The Met Service warned of thunderstorms and severe weather.
OPC lawyers Adam Ross and Michael White said the centre admitted its failings, though they said few if any other outdoor centres subscribed to the storm warning service prior to this event.
Mr Hargreaves said the OPC had a medium level of culpability in its two breaches of the Act.
Mr Ross and Mr White said the culpability level was low and that it should not be fined as the centre did not need to be deterred or denounced any further and that it had made several changes to improve safety.
But Judge Kiernan saw the level of culpability as high.
"There is a high degree of risk in this activity, and therefore there was a high degree of responsibility to your staff and those they were supervising, especially given that they were supervising children," she said.
"This was a tragedy that shouldn't have occurred and a tragedy which could have been avoided."
She said the OPC's early guilty pleas and its participation in two restorative justice conferences earlier this month were considered favourable mitigating factors in sentencing.
Parents of those killed said they were pleased with the outcome and with the restorative justice efforts of the OPC.
Jennifer Fernandes, mother of Floyd Fernandes, agreed with Judge Kiernan that no reparation would ever bring their children back, and was pleased the judge found a high level of culpability.
The college has yet to decide whether its students will ever attend the OPC again.
Elim College proprietor Luke Brough said he would find it difficult to ever send college students back, but Miss Gregory's mother Catherine Linnen said it should be up to parents to decide as many other young New Zealanders had enjoyed their experience.
OPC chief executive Grant Davidson said Elim Christian College students were welcome back at the centre but in a time that is appropriate to them.
"Families are always welcome to visit the OPC and we hope to continue that interaction."
Mr Davidson said the OPC would continue to work with the families of the victims.
OPC trust board chairman Rupert Wilson said the centre would have a careful look at the decision before commenting on it.
Mr Ross said in court that the OPC had insurance but that it would not cover its suggested maximum reparation of $330,000.
Department of Labour central region health and safety services manager Brett Murray said lessons should be learned from the tragedy.
"I hope that today's outcome will encourage others in the adventure tourism industry to look critically at their operations to ensure that they and their clients are never put in a similar position," he said.
"I would urge them to start working on this today. Because this is the kind of tragedy that can happen to anyone involved in the adventure tourism industry if they don't manage workplace hazards properly."
- NZPA
