A deputy principal at an exclusive private school has resigned almost three months after her husband left the role of executive principal at the school.

St Peter's School in Cambridge today told parents Yevette Williams, one of the school's deputy principals, had resigned to do a PhD programme in education leadership, school trust board chairman John Macaskill-Smith told the Herald.

Husband and former executive principal at the school Dale Burden resigned in late May amid an investigation into bullying at the school prompted by a number of complaints to WorkSafe.

Questions were raised in early May because neither Burden nor Williams had been seen at the school since before the end of term one.

A statement from the St Peter's Trust Board issued today wished her well for the future and thanked her for her "dedication, hard work and input, particularly in the areas of teaching and learning an curriculum development".

Bullying complaints relating to St Peter's School in Cambridge were made to workplace bullying watchdog WorkSafe late last year, prompting the school to launch an independent investigation.

That was followed by the resignation of executive principal Dale Burden in late May. In June, the school's wellbeing director Micheal Brown also resigned.

Former board chairman John Erkkila earlier this year said WorkSafe had contacted the board in term one to advise that anonymous complainants had made concerning allegations of workplace bullying and that WorkSafe was making inquiries.

"Following a meeting with WorkSafe, we worked to understand the best course of action and the board engaged two independent investigators," he said.

"Those investigators have sought to understand what may or may not have occurred. Those investigations are not yet complete, but I want you to understand that this issue is being taken incredibly seriously."

One of those investigations was being headed by former chief judge of the Employment Court Graeme Colgan who was due to report back to the board in about a month.

However, WorkSafe's health and technical services manager Api Poutasi last month said it had completed its work with the school after six months of involvement.

"The school's Board of Trustees has implemented a number of improvements, including new policies and procedures relating to staff wellbeing. These improvements have satisfied WorkSafe that staff wellbeing will be looked after, and no further action or involvement is needed from WorkSafe," he said.

He said the organisation's team of specialist health inspectors had been involved with the school after receiving an initial complaint and spoke with current and former staff about their experiences; reviewed documents, policies and procedures; and worked with the board.

"WorkSafe would like to commend the workers who raised concerns and acknowledge how their actions have led St Peter's School Cambridge to recognise an issue and take positive steps to look after the health and safety of their staff," Poutasi said.

Macaskill-Smith, who was appointed to the school's trust board in December and was appointed chairman last month, said the school had been focused on improving support for staff, updating policies and being more open about decisions.