A statement from the Cabinet Office announcing the move said: “The Prime Minister has concluded that there is a need for fresh official leadership at the Department for Education”. The 58-year-old was due to step down next Spring. He will be replaced on an interim basis by his second-in-command, Susan Acland-Hood, a former chief executive of HM Courts and Tribunals Service who was brought into the Department for Education last week to help handle the crisis.
Mr Slater’s successor is set to be appointed “in the coming weeks”, the Department said.
He is the latest senior civil servant to be ousted by the Government under Mr Johnson.
Cabinet Secretary Sir Mark Sedwill is also stepping down, as is Sir Simon McDonald at the Foreign Office.
And Sir Philip Rutnam stepped down amid a bullying row with Priti Patel in February.
Mr Johnson yesterday blamed the exam chaos on a “mutant algorithm” used to calculate grades, which was found to bias against overachieving state pupils.
The Prime Minister, addressing pupils at a school in Coalville, Leicestershire, acknowledged that the situation had been “stressful” for those awaiting A-level and GCSE results.
“I’m afraid your grades were almost derailed by a mutant algorithm,” he told them.
“I know how stressful that must have been for pupils up and down the country.
“I’m very, very glad that it has finally been sorted out.”
But Labour accused Mr Johnson of trying to avoid taking responsibility for a “shambles” caused by his Government’s “incompetence”.
Shadow education secretary Kate Green said: “Boris Johnson is shamelessly trying to avoid taking responsibility for the exams fiasco that his government created.
“Responsibility for this shambles lies squarely with Downing Street and the Department for Education, who set out how they wanted the algorithm to work and were warned weeks in advance of issues, but repeatedly refused to address the problems they had created.
“It is this Tory government’s incompetence that is to blame for the exams fiasco.”
Kevin Courtney, the joint general secretary of the National Education Union, said: “It is brazen of the Prime Minister to idly shrug away a disaster that his own Government created.
“Parents, students, teachers and heads will be horrified to see the leader of this country treat his own exams fiasco like some minor passing fad.
“The public will not easily forget the emotional rollercoaster of this year’s results season. It is certain to put a long-lasting dent in the Government’s reputation on education.”
Dave Panman, the head of the FDA civil servant union, accused the Government of making Mr Slater a “scapegoat” for the crisis.
“It is absolutely clear this govt views civil servants as nothing but scapegoats, political pawns there only to shield ministers from accountability,” he told the BBC.
Mary Bousted, the joint general secretary of the National Education Union, said: “It’s just a scorched-earth policy for civil servants.
“The ministers who should be resigning because of their political decisions have just refused to take responsibility and are laying into these civil servants, the unfortunate fall guys and gals for ministerial incompetence.”