The National Association of Head Teachers said the speedy collapse in Dunmore junior school's status illustrated the vulnerability of schools and headteachers in an increasingly high-stakes education system.
Since its long-standing head Eric Bird departed in 2000, the school in Abingdon, Oxfordshire, has had 13 headteachers, 10 of whom left within three years.
Darren Kenyon, the latest permanent head to be appointed, was placed on indefinite sick leave this month after a year at the school. He is now believed to be considering legal action.
The school gained beacon status in 1999 after being listed as one of the most outstanding schools in Britain.
But an Ofsted report published earlier this year placed the school in special measures, blaming "substantial disruption in leadership" for its decline.
Parents have blamed Oxfordshire county council for the school's "revolving door" problem.
Aileen Jones, 40, whose 11-year-old daughter Abigail attends Dunmore, said:
"The stability for the school and the kids has been sacrificed because of things going on behind the scenes."
But, John Mitchell, assistant to the council's children's services director, said a range of factors were to blame, including "the dwindling pool of aspiring and suitably qualified headteachers".
Many of the heads had been able to work only for limited periods because of commitments to the authority and other schools.
"Not all our schools will, necessarily, improve all of the time," Mr Mitchell said. "There will always be some ebb and flow."
Mr Mitchell hinted that the school's governors were also to blame.
"Appointments are ultimately a matter for the governing body which may, on occasions, proceed against the advice of the authority," he said.
The local NAHT also blamed the governing body, saying that it had neglected to appoint several strong candidates which it interviewed because they wanted a greater say in running the school.
The association said governors had gone against its advice by appointing four assistant heads as acting heads on a rotation system over four months in 2003.
Mick Brookes, NAHT general secretary, said Dunmore's difficulties also reflected national problems in retaining heads at a time when school leaders risk losing their jobs at the first sign of failure.
The NAHT published figures earlier this year suggesting that up to half a million children were in schools without a permanent head.
"This is the extreme end of what is happening nationwide," Mr Brookes said.
"We know of heads who have walked into schools on Wednesday thinking everything was fine, had a visit from inspectors, and then been considering their position by the weekend."
Oxfordshire council said Dunmore's new head, Martin Lester, was "temporary but indefinite". The school's governors refused to comment.
News 6, Leader 22