Barry Sheerman, chair of the Commons education select committee, anticipated Alan Johnson’s departure, Labour’s fifth change of education secretary in six years. “A school or an academy or a college that was changing its leadership as regularly and that had total churn in terms of the middle managers ... would be put in special measures immediately,” he said last week.

Labour did get off to a steady start in 1997 with David Blunkett, one of the longest ever serving education secretaries, who saw out Tony Blair’s first term as Prime Minister. But since then a voluntary resignation, forced reshuffle, weak performance and wholesale Whitehall reorganisation have led to six years of unprecedented instability.

Estelle Morris, the former schools minister, was appointed to the top job from within after the 2001 general election, in the hope that she would be there for the long term. Just 16 months later the teachers’ favourite had resigned, dogged by the A-level marking controversy, a failure to hit numeracy and literacy targets, criminal record check delays and her intervention in the case of pupils who made death threats to a teacher.

Charles Clarke followed. With David Miliband, now the Foreign Secretary, they became a popular duo providing much-needed intellectual ballast to the department. But Mr Clarke was moved to the Home Office after Mr Blunkett’s resignation and a disappointed Mr Miliband went to the Cabinet Office. Then came a very underwhelming Ruth Kelly.

The four education secretaries appointed since 2001 served an average of 18 months each, compared to a 31 month average for the 12 from 1970 to 2001. Mr Johnson’s reign was the shortest at 13 months and, not surprisingly, he failed to make a big impression.

The former postman guided the hugely controversial Education and Inspections Act through the Commons just three weeks after starting the job, though he needed Tory help to face down a Labour backbench rebellion over trust schools.

Then he oversaw the introduction of the progress test policy, the idea of raising the compulsory education and training age to 18 and some populist interventions over the history and English curriculum.

But it was Mr Johnson’s personal ambitions for the deputy Labour leadership and leadership rather than policies that made headlines.

John Dunford, the Association of School and College Leaders’ general secretary, agreed there have been far too many education secretaries, but was pleased this Government reshuffle, unlike the previous two, would allow some continuity, with the majority of the junior ministers staying put.

Lord Adonis, as Tony Blair’s former in-house education adviser, might have been expected to go. Instead, the new “inclusive” Prime Minister’s Government includes the peer and Jim Knight, who retain their posts as schools’ ministers.

Beverley Hughes, the children’s minister, also stays and has the new right to attend Cabinet for social policy talks. But Parmjit Dhanda, her former deputy, is replaced by Kevin Brennan from the Whips office. He used to teach economics at Radyr comprehensive in Cardiff.