Part-time pupils who are overlooked by local authorities risk becoming "vulnerable to abuse", according to the chief inspector of Ofsted.
Sir Michael Wilshaw warned of "invisible" pupils who were unable to attend full-time education and urged "everyone" to take "greater responsibility for knowing where they are".
Too often, children and young people who receive only a part-time education, or who have none at all, can become invisible to the local authority.
This can be a safeguarding as well as an educational matter. If no-one in authority knows what education these children and young people receive each week, or whether they even attend, they not only miss out on education but can be vulnerable to abuse.
Everyone must take greater responsibility for knowing where they are."
Pupils who do not attend school in the traditional way are at risk of becoming "invisible", Ofsted's chief inspector has warned.
In a report into part-time pupils, Ofsted found many local authorities did not know how much education children who had been permanently excluded, were pregnant or young mothers, those with special educational, physical or mental health needs were getting.
Sir Michael Wilshaw there is "no greater responsibility than to ensure our most vulnerable children have the best chance of a decent education".
"It is simply not acceptable that only a third of local authorities have a detailed understanding of what is happening to pupils who are not receiving full-time education. Ofsted is shining a spotlight on these failings."
Surrey Head Teacher Gail Larkin, vice-president of the National Association of Head Teachers, blamed Government policy changes for "devaluing" Religious Education as a subject in schools.
She told BBC Radio Four:
Consecutive governments have to take some responsibility for this. As the report says, the impact of major policy changes has been to convey the message that RE is of less value than other subjects, so head teachers are concentrating more on core subjects and subjects that can be measured and unfortunately I think that RE has fallen off the radar
RE is an absolutely vital subject in our schools and I've seen it decline but I think this comes back to the quality of teacher training - I was reading recently that graduate teacher programmes only have half a day of training for RE teaching.
Joanne Pearce, Lecturer in Religious Education at the Institute of Education, told BBC Radio Four:
Religious Education is crying out for trained subject specialists.
If you've been drafted in from history, geography, or sometimes PE or ICT, with the best will in the world - and lots of teachers are working very hard to do a very good job in an area that's not their specialist subject - it's very hard to deal with the complexities and sensitivities involved in religious education.
Ofsted's call for a review of the statutory arrangements for religious education has been welcomed by the British Humanist Association, which said that it is "vital that young people learn about religious and non-religious beliefs and values in an enquiring and critical way."
We have long argued that a large part of the cause of these problems is the locally determined nature of RE, leading to a huge variability of quality of attitudes towards non-religious participation and quality of syllabuses, something Oftsed has also identified as a problem.
We support Ofsted’s call for a review of the current legal arrangements underpinning this system, and would push for national determination instead. This position is supported by a huge number of those active in RE and we would urge Government to bring it about.
– Andrew Copson, Chief Executive of the British Humanist Association
Ofsted's director of schools, Michael Cladingbowl, has said that religion plays a "profound part in today's world" and that pupils "deserve much better" from their education:
Religious education in schools matters. It develops children's understanding of belief and the world in which we live.
At its best, it encourages children and young people to extend their natural curiosity and prepares them for life in modern society.
We saw some great examples of this during the survey, but too often we found religious education lessons being squeezed out by other subjects and children and young people leaving school with little knowledge or understanding of different religions.
– Michael Cladingbowl, director of schools, ofsted
More than half of England's schools are failing to give pupils good religious education lessons, inspectors have warned.
In a damning new report, Ofsted said RE is being "squeezed out" by other subjects, leaving youngsters with little knowledge and understanding of different faiths.
Schools are confused about the reasons for studying RE, the watchdog said, adding its inspectors had also found low standards in the subject, poor teaching and problems with the way it is tested.
The study, based on inspections of 185 schools, concluded that while there have been some improvements in the last decade, many RE lessons are still failing to help pupils "explore fundamental questions about human life, religion and belief".