Schools should be monitored more closely over whether they are ejecting under-performing sixth form students to boost their standing in league tables, according to a campaign group.

The Kent Education Network, which opposes grammar schools, said KCC should oversee what policies secondary schools adopted over sixth form students who did poorly in AS exams in Year 12.

Claims that some of Kent’s top secondary schools encourage under-performing students to leave are coming under renewed scrutiny.

It has emerged parents have initiated legal proceedings against a selective school in Orpington, challenging its decision to eject pupils who have done poorly in the first year of their sixth form.

The legal action may have wider ramifications.

According to The Guardian, the news of the case has triggered dozens of similar complaints from parents in other selective areas, including Kent.

Jo Bartley, of the campaign group Kent Education Network, said Kent County Council should be more pro-active monitoring schools - although the power of authorities over academies is limited.

“Some schools clearly care more about their position in the league tables than the welfare of their pupils. It is definitely something that should be monitored and KCC should be doing it.”

The court case mirrors allegations first reported last year about sixth form students being told they could not continue with their sixth form studies after either failing or getting poor grades in their AS exams.

Peter Read, a former Kent grammar school headteacher and education consultant, flagged up the issue in his blog.

He questioned the number of students who had left two of the county’s top-performing schools - Invicta Grammar School and Maidstone Girls Grammar.

He said there were suggestions - firmly denied by the schools - that students who did not secure top grades in their AS levels were being encouraged to leave as a way of the schools maintaining their reputation for ‘A’ level results.

He said: “Schools are under pressure to deliver results. What they are doing is forcing children out to achieve better A-level results. There’s something very, very wrong.”

Others say the practice is not just used by selective schools and many non-selective schools adopt similar procedures - although they often make greater efforts to keep students rather than eject them.

Legal experts say that unlike council-run community schools, academies have more autonomy when it comes to the reasons for school exclusions.