Fears have been raised about schools exploiting a loophole in league tables to temporarily take Year 11 pupils off their rolls.

A new analysis cites more than 500 cases of pupils returning to a school’s roll in the summer, having been left off for the spring term over the past two years.

It also reveals that much of the phenomenon is concentrated in just 16 schools, which account for 150 pupils that were not on any roll in the spring term, but returned to their school in the summer.

Quick read: Heads warn of confusion on off-rolling

Need to know: What is off-rolling?

Ofsted: How we will judge off-rolling schools

This would mean they were not included in the spring school census and were therefore not part of a school’s league-table scores.

The figures could shed more light on the problem of off-rolling where schools remove pupils to boost their test and exam results.

Ofsted has vowed to crack down on off-rolling, and the long-awaited Timpson Review has also focused on the problem, suggesting off-rolled pupils could be given the right to return to their original school.

FFT Education Datalab, which produced the new analysis, said 150 of the cases of pupils returning to rolls happened at just 16 schools, where “it seems to be more than a one-off occurrence”.

A new post by Education Datalab’s Dave Thomson said: “Of course, it is convenient that none of these pupils would be included in their schools’ performance-tables data, particularly when their attainment tends to be very low.”

He added: “Administrative errors may be to blame. Pupils were subsequently included in the performance-tables data at two of the schools. Presumably they were added back during the autumn checking exercise.

“There might be good reasons why this might have happened at the other schools…But what it perhaps shows is that there might well be loopholes to exploit if performance tables continue to be based just on pupils in Year 11 in the spring school census.”

He added that it was possible that the pupils may have left and returned to the same school.

“This might include going overseas for a short time or perhaps taking up a placement in the independent sector, eg, alternative provision.

“But if these factors were affecting Year 11 pupils, might we also expect them to affect Year 10 pupils at the same schools?

“Although there were 150 Year 11 summer returners at these schools, there were fewer than six Year 10 summer returners.”

Mr Thomson said the “strange phenomenon” was extremely rare with 280 cases in 2017 and 240 cases from a national cohort of about half-a-million.

Regulator Ofsted has vowed to crack down on off-rolling through its new inspection regime.

Any school found to have met the inspectorate’s definition of off-rolling is likely to have its leadership and management rated as inadequate.

The new inspection framework is set to launch in September. However, Ofsted has already identified off-rolling at three schools under its current inspection framework.

Two schools, Harrop Fold, from TV’s Educating Greater Manchester series, and Shenley Academy in Birmingham were rated as inadequate, but Discovery Academy in Stoke-on-Trent was still judged to be good overall.