As many as 100,000 children could be missing from the education system, a new report has concluded.

Published on Wednesday, the government-commissioned study found that the reasons for children missing school varied from low attainment to bullying, with absences lasting as long as two years.

Conducted by the National Association for the Care and Resettlement of Offenders, the research found that children in care were most likely to miss school.

It noted that local authorities have no legal obligation to inform other authorities when they are sending a child into foster care in a new jurisdiction.

Schools were found to be reluctant to take on children considered disruptive or unlikely to achieve academically due to their need to maintain their position in the league tables.

Of the young people referred to Youth Offending Teams, 41 per cent were found to have truanted regularly, with disaffection at school cited as a key indicator.

As many as 60 per cent of YOT offenders were found to have special educational needs.

The report concluded that the government should offer a more flexible national curriculum, with emphasis both on academic and vocational subjects.

Funding should "follow" the child rather than be retained by the school, with earlier welfare-based support for children with educational and behavioural difficulties, Nacro concluded.

"Youngsters involved in crime and anti-social behaviour are more often than not children who have, for whatever reason, missed out at school," said Craig Harris, director of education and employment at Nacro.

"An education that is both meaningful and appropriate is vital in providing a sense of worth, in enhancing life opportunities and in giving children both a stake in their own futures and in the future of the country.

"If we are to tackle the problems of attendance, education provision should be more relevant to the needs and abilities of all children, regardless of whether they are academically suited or gifted practically.

"But if attendance problems do occur, agencies need to be better at working together to make things right.

"The limits of a punitive approach to truancy have become all too apparent - positive and constructive intervention is the key to facing down these difficulties, not punishing parents."

The report was welcomed by education minister Ivan Lewis, who pledged that "comprehensive action" was being taken.

"The government is determined to tackle the causes of children missing education, and intervene early and positively with those at risk of doing so," he said.

"The green paper will deliver radical reform to children's services which will ensure that no child slips through the net.

"Comprehensive tracking systems will identify children who might be missing out and we will overhaul information-sharing between professionals to better support these children.

"Flexible learning and vocational education in our schools is keeping more children engaged with the national curriculum, with GCSEs in vocational subjects and work-related learning in the classroom.

"And the Behaviour Improvement Programme has introduced alternative education from the first day for children permanently excluded from school."

Lewis also cautioned that "estimates on the numbers of children missing education should be treated with caution".