More than a third of councils in England fail to monitor children who are not receiving an education in their area, despite a government target requiring them to.
And more than half do not keep a record of children who have left education without a known destination, according to the study for the Department for Education and Skills.
Concerns about children missing school intensified last year after the Metropolitan Police discovered that 300 African schoolboys had gone missing from schools in London during three months in 2001.
The DfES is to introduce a statutory duty to monitor children from 2007.
● Children Missing Education