One in 20 children in England is in a school that has not been inspected for more than 10 years, the BBC has found.
There are 1,010 “outstanding” schools that have not had a visit from Ofsted in a decade – up from 296 in 2017.
Inspecting all schools would ensure they were not “failing or at risk of decline”, the National Association of Head Teachers (NAHT) said.
The Department for Education (DfE) plans to lift an exemption on routine inspections for outstanding schools.
It has been in place since 2012 but watchdog Ofsted called for it to end amid concerns about falling standards.
The NAHT said parents would find it harder to compare schools without recent reports available.
Meanwhile, the Labour party has said it would scrap Ofsted if it won the next general election.
Analysis by the BBC of the official data revealed the longest schools had gone without inspection was now 13 years.
There were 24 schools that had not had an inspection since September 2006, all of them graded “outstanding”.
The latest data showed more than half of previously outstanding schools lost the top grade at their most recent inspection.
There were 56 schools that were previously graded outstanding that dropped to the lowest mark, “inadequate”, in Ofsted reports over the past five years. Another 159 dropped to “requires improvement” while 1,203 went from outstanding to “good”.
‘Many schools may have changed completely’
Only one member of staff at Combs Infant School was there when it was last inspected on 11 September 2006.
The 40-pupil school in Derbyshire was graded outstanding by Ofsted and has gone the longest of any in England without re-inspection, with 23 others last inspected in the same month.
There is no reason to believe it would have slipped down the rankings but its head teacher, Rosemary Cook, said the time had come for all schools to be treated the same.
“Ofsted regularly reviews outstanding schools, looking at attendance, data, results and whether there have been complaints from parents,” she said.
“However, many schools may have changed completely over 13 years.”
‘Forced to close’
Rebecca Bailey from Jarrow said she believed every school should be inspected regularly.
The mother-of-four has been among parents campaigning against the planned closure of South Shields School in 2020 after it was rated “inadequate” by Ofsted. The Regional Schools Commissioner was unable to find a sponsor to help it convert to an academy so South Tyneside Council took the decision to close it.
Miss Bailey said: “We see schools forced to close due to inadequate ratings… while outstanding schools go uninspected due to their Ofsted grading.”
There are 21,951 state-funded schools in England that come under Ofsted’s remit for inspection.
Almost a third of children in Trafford, Greater Manchester, went to a school that had not been inspected for a decade or more. The data showed 39 of its 94 schools were graded outstanding, with 24 of them having not had an inspection since at least 2009. Trafford Council declined to comment on the DfE’s change of policy on inspections.
In York almost a fifth of children went to schools that had not been inspected for more than a decade. The city council said 90% of children were at good or outstanding schools.
Jonny Crawshaw, a councillor in the city, said statistics on good and outstanding schools could “mislead” parents due to the long gap between inspections.
The father-of-two said: “The inspection framework and the way that Ofsted grades schools has changed over the past decade.
“Most parents will just want to know that their local school is good and that their children will be happy and fulfilled there.”
‘Happiness more important’
Madeleine Holt, co-founder of the campaign group Rescue Our Schools, said parents considered more than inspection reports when choosing a school.
“Some parents value schools being close by, good teaching and contact with parents more highly,” she said. “Personally I think there are so many other factors that are more important, such as the happiness of your child, their mental health and the kinds of people they become as a result of their education.”
Nick Brook, deputy general secretary of school leaders’ union NAHT, said the exemption for outstanding schools had acted as “a brake” on improvement.
“We have heard from head teachers who have taken over previously outstanding schools and have faced considerable resistance to change from all quarters, for fear of disrupting the apparent winning formula,” he said. “It has meant that outstanding schools have not had that official, external validation of continued excellence, which has made it harder for parents to compare relative strengths when choosing a school for their child.”
A spokeswoman for Ofsted said the watchdog had been calling for the exemption to be lifted and was pleased by the DfE’s announcement.
“Although some schools may be exempt from routine inspection, they are not exempt from accountability,” she added.
“Performance data is published for all schools every year, providing transparency on schools’ performance. Ofsted has also always had the power to inspect any school, exempt or otherwise, if it has concerns – and we have done so.”
A DfE spokesman said: “The department will shortly consult on how best to bring outstanding schools back into a regular cycle of inspection, so that schools and parents can have the up-to-date information they deserve about the performance and quality of the school.”