The head of Ofsted has warned that schools “off rolling” pupils can have dire consequences and leave young people vulnerable to gangs.

Amanda Spielman said that being removed from school can be the start of a “downward spiral”.

The chief inspector of schools told town hall bosses at a conference today that Ofsted’s new inspection regime would look to address schools putting “exam performance and league tables over the needs of individual pupils.”

The new framework is set to give more weight to a school’s curriculum and give less weight to exam results. The inspectorate has also promised to have a sharper focus on off rolling.

Speaking at the National Children and Adult Services (NCAS) Conference in Manchester Ms Spielman said: “For too many children, falling out of school is the start of a downward spiral.

"Their future becomes uncertain. And, for your part, these children are increasingly difficult to keep track of. We often talk about children going ‘under the radar’; a cliché, but so apt here.”

She also warned that options for pupils who fall out of education are slim with many PRUs and alternative provision providers being “chronically over subscribed.”

And she told council staff that children can also end up in unregulated or unregistered education.

She added: “Once children are out of school, they are unlikely to be taught for as many hours a day as they would in a school. What happens to children outside this time? Who are they associating with?

“We know that gangs are calculating and clever. They target vulnerable children wherever they are. As the St Giles Trust recently reported, the majority of children involved in county lines exploitation seem to be outside mainstream education.”

She also warned that gangs can target pupils at private schools.

Earlier this week Ofsted’s regional director for London Mike Sheridan raised concerns about gangs getting pupils to take knives into schools with a zero tolerance approach in an attempt to get them excluded.

Last month a children’s charity and a group of MPs warned that pupils who have been excluded from school may be at serious risk of being sucked into knife crime and gang violence.

A survey of English local authorities by Barnardo’s and the All-Party Parliamentary Group on Knife Crime found that a third have no free places for excluded students in pupil referral units.

In today’s speech Ms Spielman also voiced concern about the increase in the number of children being home educated and repeated Ofsted’s support for a register of home education run by local authorities.

She said: “The vast majority of home educators are well-intentioned and do a good job. But just as some schools struggle to cope with certain pupils, some parents struggle, too.

"They mostly aren’t qualified teachers and their child may have complex needs.

"At the other end of the scale, as we have highlighted, there are some who exploit home-schooling legislation as cover for using provision that doesn’t have to meet our national expectations for all children.

“The crux of all this is that it becomes incredibly difficult, for you, for local authorities, to know whether children are safe and getting a decent standard of education.”