Ofsted this week swooped on Portsmouth in its second inspection blitz on a local authority area where it believes schools are "underperforming". But concerns have emerged that the watchdog is basing the selection of its town hall targets on out-of-date figures and even political considerations.
In Derby, which became the first council to receive a mass inspection of its schools in January, local critics have argued that the city was singled out because of its opposition to the government's forced academy conversion programme.
The claim comes shortly after chief inspector Sir Michael Wilshaw revealed that the watchdog now wants to extend its role beyond inspection into school improvement, prompting fears of a conflict of interest (see panel, left).
When Ofsted announced that Derby would be the first area to receive a wave of simultaneous school inspections, the rationale seemed straightforward. The East Midlands city came second to last in a table published in the inspectorate's 2011-12 annual report, which ranked councils according to the percentage of pupils attending "good" or "outstanding" primaries - just 43 per cent in Derby's case.
Ofsted said its targeting was based on current figures. But the simultaneous inspections of 10 Derby schools in January painted a more positive picture. It concluded that one was outstanding, six were good and just three required improvement. It also found that the local authority had improved its challenging of school performance and was developing promising partnerships with schools, but needed to do more and achieve greater consistency.
"The figures that Ofsted has used were actually out of date," Martin Rawson, Derby City Council's cabinet member for children and young people, told TES. "The statistics were from last year. The current figure is that 65 per cent of schools are good or better when you take into account inspections during the autumn term, and with the latest inspections that is probably going to go up even further."
The watchdog said it selected Portsmouth because "the most recent published data" showed that only 34 per cent of its secondary pupils and 53 per cent of primary pupils attend a "good or better school". But the statistics - which place the city eighth from bottom nationally on the primary measure - have also been taken from Ofsted's annual report last year.
And once again the authority concerned has revealed that they are out of date. According to Portsmouth City Council, 53.5 per cent of its secondary and 65 per cent of its primary pupils are attending good or outstanding schools.
In Derby, some claim other motives were behind Ofsted's five-day visit in January. In October, education secretary Michael Gove revealed he had written to the city's MPs asking them to speak to the council because "local forces of conservatism" had "worked against reform and have thrown every possible obstacle in the path of potential academy sponsors and free school founders trying to make a difference".
Mr Gove's intervention followed the decision by the council's Labour administration, which took over last May, to support schools that did not want to be forced into becoming academies. Dave Wilkinson, Derby secretary of the NASUWT teaching union, believes that the council's stand against forced academisation prompted the Ofsted inspection.
"It has damaged morale," he said. "It is almost as if the whole of Derby is being singled out unfairly because of the decision the authority has taken to try to halt the tide of academy conversion."
Sir Michael announced a series of five local authority inspections this term to find out why standards in particular areas are "so low" and to assess the level of support and challenge councils provide to schools. The watchdog said it would not reveal whether it would be conducting a full inspection of Derby City Council's education services until it had finished consulting on its plan to bring back such inspections.
"The (local school inspection blitzes) are based on our latest data to be published," an Ofsted spokeswoman said. "Ofsted does not have an agenda as far as academies are concerned and in Derby the inspections are not in any way linked to academies."
The news that Ofsted now wants to improve schools as well as inspect them has raised fears about a conflict of interest at the watchdog.
In November 2011, Sir Michael Wilshaw told the Commons Education Select Committee that: "Once Ofsted gets involved in the improvement process then it inspects itself and that would be silly."
But last week the chief inspector told the same MPs that he had had a rethink. "I have had a bit of a Damascene moment," he said. "I think we have a part to play.
"We have got a moral responsibility to try to help schools to improve because, quite honestly, there is very little else out there. If you are a school in a poor local authority area, what are you going to do to get that help and advice?"
Ian Mearns MP suggested that this "power grab of local authorities' school improvement role" could undermine local democratic control, and oversight, of education.