Schools with poor Progress 8 scores are nine times more likely to be given a poor Oftsed rating, according to a new analysis, published ahead of the inspectorate's expected proposal to shift the focus away from exam results when rating schools.

Research by Education Datalab and the Association of School and College Leaders, based on data from last year, found that 37 per cent of schools with “well below average” Progress 8 scores were rated as "inadequate". That compares with 4 per cent of schools with “well above average” scores, 3 per cent of those with “above average” scores and 4 per cent of those with “average” scores.

Some 67 per cent of schools with “well above average” progress reports were rated as “outstanding”.

“There is a strong relationship between P8 scores and inspection ratings,” write Philip Nye and Steve Rollett in a blog post, published on Thursday.

“It seems to be the case that those with average P8 scores…won’t get outstanding ratings, for example, bar very exceptional cases.”

The analysis comes as Ofsted was set to announce a new approach to judging schools, which would place less emphasis on results, and which has been seen as a move to crack down on “exam-factory schools”.

In a speech in June, chief inspector Amanda Spielman said that “inspection and performance tables should complement rather than intensify one another".

"Each have good consequences, but also some unintended effects,” she added.

Progress 8 was intended to be a fairer way of holding schools to account than the old 5 A*-C measure, but studies have warned that it is often skewed by the make-up of students in a school's roll.

Research by Cambridge Assessment, published last month, found that schools with lower-performing students are “systematically penalised” by Progress 8, even though the measure is meant to be based on improvement from previous results.

The paper notes that differences in schools’ Progress 8 scores “mainly reflected the student make-up of the school”.

And headteachers in the North West of England have claimed that Progress 8 penalises schools in white working-class areas, warning it could create “wastelands” of schools deemed to be failing.