School leaders who work as Ofsted inspectors should refuse to be complicit in the watchdog's "reign of terror" and hand in their badges, the sister of a headteacher who took her own life has said.
Ofsted gave the school the lowest possible rating, despite being good in every category bar leadership and management, where it was judged "inadequate".
Ms Perry's sister, Professor Julia Waters, argued the single-word assessment "destroyed Ruth's career, her world, and her sense of self".
Speaking at the National Association of Head Teachers' (NAHT) annual conference on Saturday, Prof Waters urged reform of the "flawed, inhumane" inspection system.
Delegates, who observed a minute's silence in memory of Ms Perry, also backed an emergency motion calling on members who also work as inspectors to stop working for Ofsted.
Prof Waters told the conference in Telford: "I lost my little sister Ruth fifteen weeks and six days ago.
"But in fact I lost her as I'd always known her - happy, confident, caring, strong, determined - fifty-four days before that, when three Ofsted inspectors pronounced - on frankly flimsy grounds - that Ruth's leadership and therefore her school, were inadequate.
"The injustice of that one-word judgement destroyed Ruth's career, her world, and her sense of self."
She said: "We had to speak out because we want no other family to experience the pain that we have felt.
"We had to speak out because a terrible injustice has been done to my sister.
"Ruth was not an inadequate headteacher."
Ofsted chief inspector Amanda Spielman has said previously she has no "reason to doubt" the inspection before the death of Ms Perry and that the "findings were secure".
She has also defended Ofsted's one-word assessments, which have been criticised for being too simplistic, arguing they are easier for parents to understand.
Education Secretary Gillian Keegan has also said she fully supports the approach of providing a clear one-word rating to help inform parents' decisions.
But addressing hundreds of school leaders, Prof Waters said: "Take down your banners and write to parents to tell them that you're doing this and why you're doing it.
"We all know parents deserve better than misleading, dangerous single-word judgements.
"So stop promoting them."
'Hand in your badges'
She added: "How many of you in this room serve as Ofsted inspectors as well as being headteachers?
"No doubt you're doing your best, but you're working within a flawed, inhumane system.
"So follow the examples of Martin Hanbury, Andrew Morrish, and others.
"Hand in your badges. Refuse to be complicit in Ofsted's reign of terror.
"I call again on Ofsted and the government to show some humanity and sensitivity, to recognise the urgency and the severity of our concerns."
Meanwhile, a school in Cambridge is set to take Ofsted to court for not following the correct procedures after it was downgraded from "good" to "inadequate", the lowest possible rating, over its safeguarding systems.
But defending the finding, an Ofsted spokesman said: "Ensuring that children are safe in school is one of the most important elements of our inspections.
"We only give an inadequate judgement to a school for safeguarding reasons if we have serious cause for concern."
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