Ken Boston said officials must take responsibility when things go wrong
The head of the exams watchdog in England has resigned over this summer's Sats test fiasco.
Dr Ken Boston, head of the Qualifications and Curriculum Authority, has stepped down ahead of a report into the chaos.
Hundreds of thousands of pupils' test results were delayed and this year's league tables have been postponed.
Dr Boston, who had held the post since 2002, said his resignation followed the "delivery failure" for the tests.
"I have always believed in public bodies and public officials taking responsibility when things go wrong," said Dr Boston.
On Tuesday, Lord Sutherland is due to publish the findings of his inquiry into what caused the delays and confusion with the tests taken by 11 and 14 year olds.
The exam chief is the latest casualty of the administrative failures that affected primary and secondary school tests.
ETS Europe, the private outsourcing company hired to adminster the tests has seen its contract terminated.
Half of the tests themselves are being scrapped - with the Children's Secretary Ed Balls having announced in October that there will be no more compulsory Sats tests for 14 year olds.
If Lord Sutherland produces a damning report into what the government calls "severe problems" with the tests, then it could raise the prospect of further heads rolling.
The Qualifications and Curriculum Authority and its testing arm, the National Assessment Agency, were responsible for hiring the US-owned contractor.
Lord Sutherland's report will seek to establish what caused the problems that saw so much confusion over the tests - and why it appeared to take so long for a response.
Head teachers, teachers and markers had been warning of problems with the organization of this year's test from the spring.
In May, MPs in the House of Commons had said the tests had become a "shambles" - long before the scheduled results date in July.
Following the missed deadlines, Dr Boston appeared before a committee of MPs in July and assured them that all the tests taken by 11 year olds had been marked.
However a photograph sent soon after to the BBC News website showed boxes of unmarked test papers still lying uncollected in a Lancashire primary school - prompting accusations from opposition parties that the test authorities had lost control.
Australian-born Dr Boston had faced intense pressure in the wake of the test problems.
But his decision to quit ahead of the inquiry report has been regretted by teachers' leaders.
"It is a tragedy for the education system that Ken Boston has felt it necessary to resign," said John Dunford, general secretary of the Association of School and College Leaders.
"He has consistently spoken out about the shortcomings of the bloated testing and examinations system in England, describing it as a 'cottage industry'."
The acting leader of the National Union of Teachers, Christine Blower, said that Dr Boston had been the "victim of an entirely unviable, unwieldy and unmanageable system".
A spokesman for the Department for Children, Schools and Family said that it would be "inappropriate for ministers to comment on any issues related to the summer's delays until the Sutherland report is published".
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