Concerned parents of pupils at St Kentigern College wrote to the private Presbyterian school last year urging its principal to reconsider running the "very dark, brutal and gratuitous" musical Sweeney Todd as it had "no redeeming" features.
The revelation comes after two teenage boys' throats were cut on opening night of the production when a real razor wrapped in duct tap was used as a prop.
However, parents spoken to by the Herald were adamant the letter - dated September 17, 2015 - was not spurred by any concerns over health and safety at the show, but questions over how the gruesome musical aligned with the school's Christian values.
A copy of the letter - and the school's response - has been given to the Weekend Herald.
"Apart from the great music - there are no redeeming characters or themes in the musical and the key themes are revenge, gruesome deaths, rape and betrayal," the letter, signed by 28 parents, said.