The two 16-year-old actors were rushed to Auckland City Hospital on Wednesday night after sustaining the injuries during a performance of "Sweeney Todd: The Demon Barber of Fleet Street" at St. Kentigern College, a private school in Auckland, the New Zealand national broadcaster reported.
One boy had serious and the other moderate injuries, but both were discharged from the hospital Thursday, TVNZ reported.
CNN contacted the school but did not immediately hear back.
In comments broadcast on TVNZ, school head Stephen Cole told reporters Thursday that the students were wounded by a prop razor "covered in all sorts of duct tape and foam and paper."
"It's a razor, but it's been filed down and bound with various things," he said, adding that the prop did not have a sharp edge and had been used during rehearsals without any problem.
"It was an unfortunate isolated incident which we're of course very disturbed about," he said.
Asked by a reporter whether a plastic prop blade should have been used instead, he replied, "In hindsight that may be a reasonable point."
"It was deemed important to make it as realistic as possible," he told reporters.
The musical tells the story of the "demon barber of Fleet Street" in Victorian London, who kills customers by slitting their throats, then disposing of their remains as filling for pies.
The school's promotional materials for its production featured an image of a bloodied straight razor resting on a pie.
Police and workplace safety officials were investigating, but the school was confident no shortcomings would be found, Cole said, according to TVNZ.
In January, an Italian actor was killed in a botched hanging scene
in an experimental theater performance in Pisa, and the following month a Japanese actor died when he was stabbed in the stomach with a samurai sword