Parents of children hoping to get into Tiffin Boys School “are considering legal action” over the “unfair” entrance examinations.

More than 1,000 boys took exams on September 27 to win one of 140 places at the grammar school, ranked as the eighth best selective secondary in the country.

But fears have been raised that boys who were not able to take the exam after the registration was brought forward have been handed an unfair advantage after more than normal were offered a late entry test on December 7, before the school places are offered next March.

A private tutor, who did not wish to be named, said she knew some parents who were considering legal action after their children sat the first exam.

She said: “Children have gone back to school and told their friends, so they now know what the test is.

“Plus they have also had three months more worth of studying. Parents are mad about getting their children in.”

Tiffin School declined to answer questions, or say how many children were affected, but headteacher Hilda Clarke wrote to parents to say it was obliged by law to offer the second exam.

She wrote that late changes by the Government to the admission code in February had forced selective schools to change the dates of their examinations to an earlier date in the autumn term “causing other problems beyond our control”.

She added: “We are legally obliged to test any student who names us on the Common Application Form, hence the need to test late applicants. Many parents seem to think that the remaining weeks of practice will make a huge difference. This is not true.”

The school said it had advertised the date change but, because Kingston Council’s booklet on secondary school transition was not with parents until September, some were not aware of the need to register until after the closing date.

Councillor Andrea Craig said: “Knowing a lot of parents who go to this school, there are very few people that don’t know the deadlines of the registrations.

“It’s a very emotive issue and I do have sympathy with the parents.”

The school’s old boys include Victoria Cross recipient Douglas Belcher, Alec Stewart and Jonny Lee Miller.

Tiffin Girls’ School will also offer late 11+ exams but this year is holding two rounds of exams to test curriculum as well as verbal and non-verbal skills.