An independent investigation into allegations of misconduct at a top London state school – including safeguarding breaches, discrimination, bullying and favouritism – has found that “on the balance of probabilities” every complaint made happened.

More than 100 former students and staff at Holland Park school in west London submitted evidence to the investigation, which also considered allegations that Ofsted was misled by senior leaders and that there was “overt sexism, Islamophobia, and racism” at the school.

On safeguarding, the investigation found the school had failed to support students who had been victims of peer-on-peer sexual abuse, there were inappropriate responses to the case of a teacher who was found to have had a relationship with a pupil, and there was “exploitation” within some student-teacher relationships.

There was a culture of fear, favouritism and inequality, a summary of the 554-page report said, with staff and students publicly humiliated. Some of those who gave evidence to the investigation are still traumatised by their experiences.

On Ofsted, the report said some staff questionnaires relating to an inspection in January 2020 were destroyed, while certain students were taken off-site or told not to attend school during the inspection.

Parents with children currently at the school include the secretary of state for levelling up, Michael Gove, and former Commons Speaker John Bercow.

The complaints relate to events dating back as far as 2004, when the school was under the control of the local authority, Kensington and Chelsea, to September 2013, when it became a single academy trust, and up to December 2021.

Former head teacher Colin Hall, who left last September, said at the time the allegations began to emerge: “We don’t recognise the characterisation of the school or our leadership in the allegations raised.”

A statement issued by the board of governors on Wednesday, which accompanied the summary of the report, said: “The investigator’s view, based upon extensive and corroborative evidence provided during interviews, is that on the balance of probabilities every complaint is found to have happened.

“These include bullying, favouritism and the public humiliation of staff and students, serious safeguarding failures, dubious spending, the misleading of Ofsted, and vulnerable children and key worker children not being accommodated at the school during Covid-19 lockdowns against government guidance.”

The statement said the board, which has recently been reconstituted, “deeply regrets” that the investigation – carried out by independent investigator, Jessica Joels, of B3sixty, which specialises in workplace investigations – has concluded that these events had occurred.

“We are taking the findings very seriously. As a result, and after much consideration, the governors intend to make one referral to the Teaching Regulation Agency and will be commencing a disciplinary investigation in respect of three members of staff. All will be given a full opportunity to respond before any conclusion is reached.”

Former pupil Zahra Enver, 20, who was among those who wrote an open letter which helped trigger the investigation, welcomed the report. “We are so grateful and proud of everyone who came forward and hope this summary report can provide some healing for them.”

Former teachers Elizabeth Holland and Lara Agnew added: “All the teachers who came forward to submit evidence to this inquiry have shown extraordinary courage and taken a considerable risk in doing so.”

The Department for Education previously issued the school with a notice to improve in November 2021, highlighting financial mismanagement as well as “leaders’ excessive salaries and failure to seek prior approval from the government for ‘novel and contentious’ expenditure”.