St Kent's accepts 'life-threatening' risk to students in Sweeney Todd play

An Auckland high school has admitted putting its students at serious risk during a play performed last year, which saw real razor blades used in the shows.

Two 16-year-olds had their throats cut on the opening night of Sweeney Todd at St Kentigern College, forcing the cancellation of the following performances.

The school used real razor blades in the shows, which had been filed down and wrapped in duct tape, foam and silver paper, according to St Kentigern's Head of College Steve Cole.

But now the school has apologised after a WorkSafe investigation.

"St Kentigern accepts that it should have done more to acknowledge the seriousness of what happened immediately after the accident," Dr John Kernohan, deputy chairman of the St Kentigern Trust board, said on Wednesday.

"The injuries were not minor. The injuries were significant and life-threatening."

Reparation will be paid to those involved as St Kentigern works on a "restorative justice process with the victims of the offending", WorkSafe said.

"We have carefully considered the impact of this incident and the wishes of the three victims and their families," WorkSafe's Brett Murray said.

"The St Kentigern Trust Board has taken responsibility and accountability for its breach of the law and is taking a number of actions to address the issues that led to this serious incident. Through this enforceable undertaking a range of steps will be completed."

Professional prop suppliers told Newshub in 2016 it wasn't industry practice to use real blades in productions - particularly with a school production.

"What on earth were they doing using a real razor blade or a real knife?" Cutting Edge drama director Sioux Smith said.

"I mean, no more than you'd use a real gun! Even when we're talking big Hollywood productions, they would be using props - they would not be using the real articles."

Sweeney Todd is a musical about a barber in Victorian-era London, who murders his customers with razors and makes their remains into pies.