Ofsted has identified 300 schools with particularly high levels of “off-rolling” where pupils leave between Year 10 and sitting their GCSEs.

It found that of the 2,900 schools that lost some pupils between years 10 and 11, there were 560 where numbers were significantly above what Ofsted would expect and 300 where this had been the case for two years.

An Ofsted director said it would use these findings to ask questions during school inspections.

The inspectorate has also warned that around half of the 19,000 pupils who left a school between year 10 and 11 in 2017 did not reappear in the census of another state school.

Ofsted is responding to concerns that rising numbers of pupils are leaving mainstream secondary schools before taking their GCSEs.

Jason Bradbury, Ofsted’s deputy director for data and insight warned that some of the pupils who have not reappeared on school census data may now be attending an unregistered school or have dropped out of education entirely.

He also warned that children with special educational needs, looked after children and some minority ethnic groups are more likely to leave their school.

The Ofsted analysis published today also says that a higher proportion of schools in London are seeing movement of pupils compared to other areas of the country and that academies, particularly those in academy trusts, are “losing proportionately more pupils than local authority schools.”

Mr Bradbury adds: “Conversely local authority schools seem to be taking on proportionately more pupils.”

Ofsted has now produced a model to investigate where exceptional levels of pupils have moved.

It has found 2,900 secondary schools that lost at least one pupil, 810 that lost five or more or five per cent of their cohort and 560 where schools lost significantly more pupils than expected.

Mr Bradbury said it would raise its findings in discusisions with local authorities, multi academy trusts and to ask questions of schools in inspections.

It was reported last week that there has been a “sharp rise” in the number of pupils leaving mainstream secondary schools in England before taking their GCSEs.

Research by FFT Education Datalab sparked fresh concerns about “off-rolling” - the phenomenon of removing children from a school roll but not necessarily through formal exclusion procedures.

Researcher Philip Nye found that 10 per cent more children left mainstream secondary schools in England before the end of Year 11 in 2017 than in each of the previous three years.