Thousands of children 'missing' from education
More than 30,000 children were missing from schools in England and Wales for substantial periods of time in the 2014-15 academic year, local education authority figures show.
Of these, almost 4,000 children could not be traced by the authorities.
The National Children's Bureau said some may be at "serious risk" of abuse and exploitation, including forced marriage, FGM and radicalisation.
The Department for Education said it had issued "new guidance" to schools.
Ofsted has previously raised concerns that some missing children could be hidden away in unregistered, illegal schools.
The figures, obtained by the BBC's Victoria Derbyshire programme, show that 33,262 school-aged children were recorded as missing from education in the academic year ending in July 2015. They were collated from a Freedom of Information request to 90 local education authorities in England and Wales.
Children were recorded as "missing from education" if they were of compulsory school age, and the authorities were unable to trace them - typically for four weeks or more, or two to three days in the case of vulnerable children.