Almost a quarter of home-tutored children in Leeds receive an unsatisfactory or non-existent education, according to the first official statistics on the subject.
They show nationally nearly 10 per cent of children who have opted out of school are not receiving an acceptable education.
That rises to 24 per cent in Leeds, according to data from the Department for Children, Schools and Families (DSCF), which surveyed local authorities across England.
* Click here to follow the YEP on Twitter.
And the true figure could be far higher, as experts admit there is no way of knowing exactly how many youngsters are being home-educated – and potentially missing out on any schooling at all.
* Click here to watch latest YEP news and sport video reports.
Other areas with high rates of youngsters being unsatisfactorily tutored at home include Stockton-on-Tees, with 45 per cent, and Wolverhampton with 23 per cent.
* Click here for latest YEP news and sport picture slideshows.
By comparison, the latest Ofsted figures report just two per cent of teaching in schools is "inadequate".
* Click here to become a fan of the YEP on Facebook.
In Kirklees just 67 youngsters were being taught at home and less than 10 were receiving an unsatisfactory education.
No figures were available for Wakefield.
Brian Hogg, responsible for "education other than at school" services for Education Leeds, said it came across "quite a spectrum" of parents – from professionals with laptops and private tutors, to those who don't take it seriously.
He said: "I would say about 75 per cent of them are parents who are wanting to do well for their children."
He added: "The other 25 per cent are parents who don't take sufficient care in managing their child's education."
At the time of the survey, 140 children were known to be home educated in Leeds, 34 of those were receiving some education but not full-time, and less than 10 were receiving no schooling whatsoever.
Ten per cent were "not co-operating with monitoring so no assessment could be made" and 14 per cent had not yet been assessed.
Incredibly, there is no legal requirement for parents to register their
home-schooled child with the local authority, so many more five to 16-year-olds in the city could be missing out on a decent education.
Mr Hogg said: "We don't know how many are really out there who are being educated at home or not experiencing an education."
He added: "If a local authority doesn't know, if it can't account for all of its children then there's the potential for difficult situations to arise."
Mr Hogg said there could be "a significant number of children" who had dropped off the radar in terms of education in the city.
He added: "People coming from another part of the country with a child who's never been in school, we wouldn't get to know about them unless their profile was raised in some other way."
Graham Badman's assessment of home-education, commissioned by the Government last year, called for urgent action to improve safeguards aimed at avoiding tragedies such as those of Victoria Climbie and Khyra Ishaq, withdrawn from school by her mother then starved to death.
A system called ContactPoint is being rolled out to better track and support youngsters. And the Government is planning to make parents who take children out of school register with local authorities and give details of what they will teach.
Local authorities presently do not have to monitor how many hours a child receives.
The DSCF estimates 11,600 children are taught at home in England, but home-educator groups say it is more likely 23,000.