Education authorities across the West Midlands admitted they were unable to guarantee against sex offenders working in their schools.
The admission came as Ofsted today accused schools, councils and the Government of failing to keep children safe from paedophiles.
In a damning report, the watchdog highlights a lack of adequate record keeping in schools and town halls, making it seem the education world "does not take this aspect of the safeguarding of children seriously enough".
Education Secretary Alan Johnson immediately responded by announcing new rules to allow Ofsted to assess schools on staff records as part of routine inspections.
With fresh concern over pupils' safety, the region's authorities sought to under-line confidence in their procedures to stop sex pests working with children.
None, however, could give categoric assurance that schools in their jurisdiction were completely safe.
Birmingham, Europe's biggest education authority, even admitted there was a "small number" of people allowed to work in schools without clearance from the Criminal Records Bureau.
It stressed they were always supervised and never left alone with children.
But the authority said it would "welcome further guidance" and tightening of procedures from the Department for Education and Skills.
"This could include insuring schools notifying the LEA that all the recruitment recommendations have taken place before employment, so the LEA can maintain a database subject to auditing at any time," said a spokesman.
Education chiefs in Worcestershire said it would be impossible to ensure there were no sex offenders in its schools.
"Ultimately you can't guarantee it because you rely on other organisations such as the local police forces to provide you with that information," said a spokesman.
"It is a sad fact of life that there are potential sex offenders out there who have not committed any crime and would not show up on any database."
W arwickshire County Council added there was an issue with teachers recruited by schools before the CRB came into existence in 2002.
"You could have someone working for years and years who is a sex offender and not recognised as such."
A spokeswoman for Solihull's education department said it followed standard procedures and rules. "We do all we can," said a spokeswoman.
A statement from Coventry said: "We are confident that to the best of our knowledge no sex offenders are employed in Coventry schools," while Wolverhampton added: "To its knowledge, the Council does not employ any registered sex offenders in schools."
Meanwhile, a study out yesterday found 90 per cent of schools were ignoring new guidelines on safety when employing agency staff.
The DfES introduced the Quality Mark scheme in 2002 following the scandal of a Canadian supply teacher who admitted having sex with one of her pupils.
Concern over paedophiles in schools reached crisis point at the start of the year when former Education Secretary Ruth Kelly admitted at least 88 sex offenders were allowed to work in schools since Labour came to power in 1997.