The head of a prestigious Waikato private school who went on extended leave amid claims of a toxic culture, has resigned.

St Peter's Cambridge has confirmed today its Head of School Marcus Blackburn has resigned and already been replaced by another headmaster.

Trust Board chairman John Macaskill-Smith said in a statement to media that Jason Speedy, the headmaster of Hamilton's private primary school Southwell, will start at St Peter's at the beginning of next year.

Blackburn went on extended leave in August citing family circumstances as the reason, but some parents and ex-teachers told RNZ there was a toxic culture at the school.

In August Macaskill-Smith denied Blackburn was under investigation or facing a disciplinary process related to allegations of bullying and denied any complaints had been made about him.

Shortly after Blackburn took extended leave saying he return at the beginning of term 4, on October 14.

The sudden departure reignited concerns about the school's leadership culture and priorities with two recent ex-staff telling RNZ they raised concerns about Blackburn or other senior staff over a raft of changes at the school and what they called a "toxic" working environment.

Another two staff said they could not discuss why they left the school because they had signed non-disclosure agreements.

In September WorkSafe confirmed it had received one complaint about mistreatment of staff but it did not specify who the complaint was against, and said the notification was assessed and closed.

"Following the workplace assessment, WorkSafe was satisfied that the school was aware of the issues and was offering appropriate support to the workers.

"No enforcement action was taken, and the file was closed."

In his statement today, Macaskill-Smith thanked Blackburn for his contribution to the school on behalf of the board.

"Mr Blackburn was instrumental in leading several initiatives that will stand St Peter's in good stead as it continues to look to its future and prepare students for life, leadership, and beyond," he said.

"Chief among his achievements include the introduction and implementation of the St Peter's Seven-Year Student Journey and amplifying an educational approach that seeks to develop students holistically as learners and leaders.

"We wish Mr Blackburn all the very best for the future."

Macaskill-Smith said Blackburn had been on extended personal leave since mid-August, during which time he signalled his resignation and asked the board to keep it confidential until now.

He said Speedy had been appointed the new Head of School and would start in term 1 in 2025.

"Mr Speedy is currently Headmaster at Southwell School in Hamilton, the largest co-educational independent primary and boarding school in New Zealand.

"He was also on staff at St Peter's for 14 years as a teacher and associate principal before taking up the headmaster role at Southwell in 2016."

Macaskill-Smith said St Peter's was fortunate to have a conversation with Speedy "at the start of our planned recruitment process and after in-depth meetings, conversations and careful consideration, the board is confident Mr Speedy is the right person for the role".

"We look forward to introducing Mr Speedy to our school community and for our staff, students, and parents and caregivers."

Speedy said in the statement he was "excited to be joining the St Peter's team in 2025 and eager to contribute to the success of this great school".

rnz.co.nz