A school is more likely to remain "inadequate" if it becomes a sponsored academy, new Ofsted data suggests.
The watchdog has released statistics on the outcomes of the latest inspections for schools previously rated inadequate.
It shows that where the schools were sponsored academies that had replaced maintained schools, 12 per cent remained inadequate. But only 2 per cent of non-academy state schools received the bottom rating when Ofsted returned.
The Ofsted data, which has been published in response to a parliamentary question from Lord Hunt of Kings Heath, also reveals that 62 per cent of schools previously rated inadequate, that stayed in the local authority maintained sector, have become “good” or “outstanding”, compared with 47 per cent of sponsored academies.
Lord Hunt said: “There is a general assumption, in the government and the media, that becoming a sponsored academy is the only way to improve a school. However, this data, from Ofsted, suggests the opposite. A school is far more likely to improve its Ofsted status if it remains in the maintained sector.”
But the Department for Education (DfE) has described the analysis as “utter rubbish” partly because more than half of the sponsored academies previously rated inadequate (343 out of 557) have still not had a follow-up inspection. The Ofsted letter itself states that the inspections are “not representative of all local authority maintained schools or sponsor-led schools”.
Kevin Courtney, deputy general secretary of teaching union the NUT, added: “The government’s whole schools strategy is based on the dogmatic belief that conversion to academy status by definition improves standards.
“These latest findings show this to be nonsense. It is, in fact, the proven structural support of maintained schools which is more likely to achieve results. But the government’s educational vandalism is systematically undermining the role of local authorities in education, to the detriment of our children.”
However, the data also shows that sponsored academies previously rated inadequate are more likely to be judged “outstanding” with 6 per cent receiving the top rating, compared with 2 per cent of inspected maintained schools.
A DfE spokesperson said: “The NUT and Local Schools Network’s analysis is utter rubbish. Obviously local authority schools appear to improve quicker, because their very worst schools are taken out of their control and turned into academies.
"What’s more, 60 per cent of those schools rated inadequate under council control have not yet had a follow-up Ofsted inspection. The NUT and LSN are either being deliberately misleading, or they do not understand how the sponsored academy programme works.
"As their own research shows, academy status, under the leadership of strong sponsors, is transforming schools with longstanding educational underachievement.”