Coasting schools 'to be taken over in new drive'
New powers for the education secretary to sack heads and intervene in coasting schools are soon to be unveiled.
Coasting schools have average results which have often flat-lined over time.
Ministers would be able to force schools rated requiring improvement and missing new government benchmarks to become an academy.
More than 3,300 schools in England are labelled "requires improvement", but the plans are unlikely to cover this many schools.
Russell Hobby, general secretary of the National Association of Head Teachers, said there was unlikely to be capacity to intervene in thousands of schools, but added it was his first priority to find out exactly what the new Conservative government was proposing.
He said: "Do they really have the capacity in the system to do this? There aren't enough academy chains, multi-academy trusts, system leaders or national leaders of education to intervene in so many schools."
Before the election, David Cameron said he would wage an "all-out war on mediocrity", promising that any school that was not judged good or outstanding would "have to change".
A source close to Education Secretary Nicky Morgan said: "The first thing we will be doing is introducing an education bill, which will feature in the Queen's Speech, in order to tackle coasting schools as per our manifesto pledge. That is definite."
Under the current system, secondary schools are considered to be failing, and therefore eligible for intervention, if fewer than 40% of their students score at least five Cs at GCSE, including English and maths, and they do not meet national averages in pupil progress.
In primary schools, the threshold for intervention is if fewer than 65% of pupils get Level 4 in reading, writing and maths and a below average number of pupils make the expected amount of progress.
It is not clear exactly how coasting schools will be deemed in need of intervention, but it is understood that a new category will be devised covering schools which are rated "requires improvement" and which fail to meet a new set of standards on improvement.