Ofsted's controversial chief inspector today launched a stinging attack on heads and teachers who make excuses and complain about their jobs, saying they do not know what stress is.
England does not need school leaders whose first instinct is to blame others for failure, but those that are willing to tackle under-performance, Sir Michael Wilshaw warned.
Heads have more power, pay and freedom than ever before and should recognise the "privileged" position they are in, he said.
Wilshaw also vowed to press ahead with his proposals to raise school standards in the face of widespread criticism from headteachers.
He told a conference at Brighton College this morning that in the past, headteachers who were not prepared to tackle poor teaching were not challenged.
"We need to learn from this and challenge those who have power invested in them to make the difference, but too often make excuses for poor performance - it's just too hard, the children are too difficult, the families are too unsupportive, this job is far too stressful," Wilshaw said.
"Let me tell you what stress is.
"Stress is what my father felt, who struggled to find a job in the 1950s and 1960s and who often had to work long hours in three different jobs and at weekends to support a growing family.
"Stress is, I'm sure, what many of the million and a half unemployed young people today feel - unable to get a job because they've had a poor experience of school and lack the necessary skills and qualifications to find employment.
"Stress is what I was under when I started as a head in 1985, in the context of widespread industrial action - teachers walking out of class at a moment's notice - doing lunch duty on my own every day for three years because of colleagues who worked to rule - covering five classes in the sports hall when there was no-one to teach them.
"Stress was, in the days before local management of schools, writing letters in triplicate to the local authority asking for a brick wall to be built in the playground or for a bit of extra money to keep an excellent maths teacher - and not receiving a reply for weeks.
"I still bear the scars of those days."
Wilshaw said that times have changed, and that heads are now in charge, with better pay and more independence, power and resources than before.
"We need heads who know what a privileged position they are in now and who can use their new-found independence well - people who roll up their sleeves and get on with improving their schools, even in the most difficult circumstances.
"What we don't need are leaders in our schools whose first recourse is to blame someone else - whether it's Ofsted, the local education authority, the government or a whole host of other people."
Wilshaw told the conference that the bar on school standards must be raised.
"We must hold our nerve," he said.
"I am determined to do so as chief inspector, and not panic at the first whiff of grapeshot, some of which has whistled past my ears over the last few days."
The union passed an emergency motion which said they were "saddened and dismayed" by his approach.
The move represented a further deterioration of relations between the union and Ofsted, and came just days after the NAHT raised concerns over the variable quality of inspections and the watchdog's planned changes to the inspection system.
Proposing the motion, Mike Curtis, an Oxfordshire headteacher, had told the NAHT's conference: "Fear reigns and confidence wanes as Ofsted waves its stick!"
It is time to stand up to "bully-boy tactics", he added.
Education Secretary Michael Gove backed the Ofsted chief in his speech to Brighton College today, telling delegates: "There's been some criticism recently of the new inspections framework and the new chief inspector.
"I've listened to that criticism - I've considered carefully the arguments made - and I have to say on reflection - it's misdirected at best, mischievous at worst.
"Sir Michael Wilshaw is a visionary school leader who has spent his career in the state sector and has achieved amazing results for children from the poorest homes - when his critics achieve results like him, then I'll believe their arguments carry the same weight as his experience.
"He is determined to improve inspection, drive up standards, encourage great teaching and celebrate good leadership - he deserves the backing of everyone who wants children to succeed - and I shall do everything to ensure that whatever he wants - he gets."
Brian Lightman, general secretary of the Association of School and College Leaders, said: "Committed, hard pressed school leaders who have been working tirelessly to raise standards despite a climate of public denigration, job vulnerability and spending cuts know exactly what stress is.
"Asking the chief inspector to stop denigrating the profession and to recognise the challenges school leaders face, especially in schools in disadvantaged areas, is not, in my book, blaming others."
Dr Mary Bousted, general secretary of the Association of Teachers and Lecturers (ATL), said: "Please will Ofsted concentrate on helping schools improve and stop criticising teachers and heads.
"It is really not helpful for Sir Michael Wilshaw to rubbish the amount of stress teachers are under.
"And Ofsted is part of the problem with its continual changing of the inspections goalposts and ridiculous demands for lessons to be exciting at all times."