Number of pupils out of school for at least a month has risen
Almost 12,000 children in England have missed school for at least a month and 1,500 of them cannot be traced, statistics obtained by the Times Educational Supplement reveal.
Leicester has the highest number at 2,611 which it said was the result of a "ruthless" process to trace the whereabouts of all children.
John Broadhead, head of behaviour and attendance at the council, said other local authorities did not do as much. The council employs a member of staff just to track down missing children.
The next highest is Birmingham with 762. Kent and Bradford have 618 and 593 respectively. Some 69 local authorities said they had no missing pupils.
The Times asked every local authority under the Freedom of Information Act how many missing pupils they had recorded and how many of these were traceable.
There is no national database, but the last time the government estimated the total, at least four years ago, 10,000 children were thought to be missing.
A pupil is counted as missing if they have skipped a month at school. For some, their parents have chosen to teach them at home. Others may be in neighbourhoods where there are not enough school places or may refuse to attend school.
Patrick Leeson, director of education and care at Ofsted said children whose whereabouts were unknown were at risk of physical, emotional and psychological harm.
"Local authorities, schools and partner agencies need to share information more effectively to identify children and young people who are missing from education, particularly when their whereabouts are unknown," he said.
Linda Lewins, vice-president of the National Association of Teachers of Travellers, said many Gypsy and traveller families told teachers they were leaving, but local authorities found it difficult to discover where they were going.
A spokeswoman from the Department for Education said: "We expect local authorities to ... ensure that these children are not missing out on their education."