More than 100 schools have not had a full Ofsted inspection for almost a decade, TES can reveal, prompting fears that too much time is being allowed to elapse between visits.

According to official data from the inspectorate, 115 schools last underwent a full inspection in 2006. And more than 600 outstanding schools have not been visited by inspectors for seven years or more.

Since 2012, schools rated outstanding by the watchdog have been exempt from routine inspection. Former education secretary Michael Gove said the move would free the best schools from the “burden” of inspection. At present, inspectors return to outstanding schools only when there are parental complaints, safeguarding concerns or dramatic fluctuations in exam results. But school leaders said the new figures were cause for concern and warned that leaving schools for too long without outside assessment put standards at risk.

TES analysis reveals that the two schools waiting longest for a section 5 inspection are Combs Infant School in Derbyshire and the Compton School, a secondary in North London. The last full inspections of both institutions took place on 11 September 2006.

Rosemary Cook, headteacher of Combs, said the long period without inspection was a “double-edged sword” for the school. “It’s great being left alone to get on with the job, but also a stress for staff and governors as we await the phone call on a daily basis,” she added.

Earlier this month, Ofsted announced that from September good schools would be subject to shorter inspections every three years. At present, inspectors visit once every five years. When first suggesting the change last year, chief inspector Sir Michael Wilshaw said the five-year gap was “too long”, adding: “It’s too long for parents. It’s too long between inspections to spot decline, and it’s too long for improving schools to show that they are outstanding.”

The NAHT headteachers’ union has called for the three-year inspection cycle to also be applied to outstanding schools. But Sir Michael has insisted that, despite his desire for “all schools to be inspected routinely” once more, a change in the law would be needed in order to include outstanding schools.

Ofsted’s most recent annual report reveals that, in 35 per cent of secondaries inspected in 2013-14 which were previously rated good or outstanding, the overall grade fell to requires improvement or inadequate. The main reason, the report says, was headteachers allowing schools to “lose focus on quality - schools had simply drifted along and become out of date. Often, they had not kept up with developments in education and were not challenged sufficiently by governors or their senior team.”

Brian Lightman, general secretary of the Association of School and College Leaders, said older judgements made under an outdated inspection framework would not satisfy parents.

“The education system has changed massively since 2006. So has the inspection framework; it has changed five times since 2012,” he added. “For parents, that’s a very long time for a school not to be inspected. It’s longer than students spend at the school. Inspections in 2006 were against a very different set of criteria that has little currency now.”

Jonathan Simons, head of education at the Policy Exchange thinktank, called for routine inspections to be reintroduced for outstanding schools. “I understand why they are exempt, with the risk-based, proportionate approach to inspection, but if inspectors are going back into a formerly outstanding school because the results have dipped, it’s already too late. The longer a school is left, the more it can feel out of the loop and need reassurance that it is still outstanding.”

Earlier this week, the ATL teaching union called for the abolition of overall inspection grades. Instead, inspection teams should build a supportive “continual relationship” with schools that would only occasionally lead to full inspections, it said.

Although Ofsted’s current inspection framework states that good schools must be visited by inspectors within five years of the end of the school year in which they were last inspected, the inspectorate’s data reveals that 18 good schools which last received a full inspection in 2008-09 have not yet been revisited.

An Ofsted spokesman said the delay was because the schools had converted to academy status, but added that they would be inspected within two years of reopening as academies.

“Ofsted plans to introduce new inspections for good maintained schools and academies from September 2015,” he added. “These short, frequent inspections will focus on ensuring that good-quality provision is being sustained, while allowing inspectors to take quick action if standards are found to be declining significantly.”

The Department for Education said: “Ofsted still conducts regular risk assessment at all of these [outstanding] schools. The exemption will only apply as long as a school retains its high performance.”

`We’re always ready; that can be stressful’

When Combs Infant School in Derbyshire last underwent a full Ofsted inspection in September 2006, Christine Gilbert had just been appointed chief inspector and Alan Johnson was serving as education secretary in Tony Blair’s Labour government.

“People think being outstanding for so long sounds lovely, but it’s actually very hard: there’s nowhere to go apart from down,” says headteacher Rosemary Cook. “We’re always ready for Ofsted; that can be very wearing and stressful. The paperwork is always ready and up to date.

“But, being outstanding, we’re given some freedoms, so in that sense it’s been fantastic. Standards have been maintained and Ofsted has left us alone. We’ve still been trying new things - we’re always striving to improve.

“We are lucky in Derbyshire as we still have link advisers from the local authority who support and challenge schools without coming in - as Ofsted sometimes does - with just a data agenda.”