More than 5,000 weak head teachers are failing to do their jobs properly and blighting the futures of tens of thousands of pupils, the chief inspector of schools declared today.
Sir Michael Wilshaw warned that poor leadership affected about a quarter of England's 21,000 primary and secondary schools.
He said under-performing heads were "trotting out excuses" such as poverty and deprivation to explain away low exam grades, and they were failing to get to grips with sub-standard teaching.
Sir Michael's controversial attack came as he prepares to unveil a tough new inspection regime later this week.
He said the "satisfactory" grading used by Ofsted for years would be scrapped because it "falsely denotes acceptable provision".
Instead these schools will be judged to "require improvement".
Figures from Ofsted reveal that 23 per cent of heads missed out on a "good" rating at their last inspection.
A further one per cent were found to be failing.
At the same time, heads have benefited from pay rises with around 700 now on six-figure salaries.
"Everything flows from leadership - that just has to be said," said Sir Michael.
We are not going to improve the quality of teaching unless there is a) strong leadership and b) really strong performance management of staff.
"That is too often the case, I am absolutely clear about that.
"A whole range of issues are trotted out - it is ethnicity or it is poverty or it is background or it is years of poor performance in a particular city or region.
"We have heard them all before. We won't move forward if we don't have a no-excuses culture. "We haven't got it at the moment, we must develop it."
Sir Michael said parents were too willing to believe a school was good simply because their child liked it.
"A lot of parents will say, "Well my child is happy here'. We need to say, 'Well yes, they may be happy and relationships might be good but actually they should be achieving a lot more'," he said.