The 11-plus is unfairly weighted against children born in the summer months, a school adjudicator has said.

The Consortium of Selective Schools in Essex (CSSE) has been told its test scoring is “unfair” by the unnamed school adjudicator.

The test is said to be biased towards older children, with test entrants born in July or August at a disadvantage in terms of passing the test compared to older pupils of the same school year.

It comes after a complaint, made anonymously by a parent, was directed at Colchester County High School for Girls. Following the complaint, the adjudicator said: “A smaller proportion of summer-born girls who take the test achieve the required test scores than girls born at other times of the year.

“I consider that the admission arrangements currently in operation are unfair to girls who are born in the summer months.”

The adjudicator ruled girls taking the 11-plus at the school in September must have their scores adjusted to reflect age differences. The adjudicator’s ruling only applies to Colchester County High School, although other Essex grammar schools share the use of the same test, including four in Southend.

The CSSE 11-plus test has been used by the ten Essex grammar schools since 1997, and although most 11-plus tests adjust test scores to compensate for age differences, this test does not. In 2017 only 19 per cent of pupils born in July or August achieved a test pass mark for the grammar school, compared to 35 per cent of children who were born in September.

Parent Neil Reeve, from Westcliff, whose son narrowly missed out on a pass mark, said: “My son’s a clever lad and was just a couple of marks shy of a pass. We couldn’t believe grammars in our area don’t recognise that some children are almost a year behind others when it comes to development and maturity. That development makes a big difference when it comes to dealing with the extra study and pressure that the 11-plus puts on pupils.”

Mr Reeve added: “He’s happy at another school now and doing very well, but at the time we felt so sorry for him as the odds seemed to be stacked against him.”

The decision raises the question of whether the ruling will be applied to other Essex grammars.

James Courtenay, Southend councillor responsible for education said: “I expect the consortium will review the decision of the schools adjudicator and take the necessary action as it is required to implement this judgement and consider the wider implications of that judgement. Although this is for a particular school, what argument could one school use that another didn’t?

“The consortium has always made a lot of effort to try to make tests as fair as possible. There used to be verbal reasoning but that was scrapped because the least able could be tutored.I have faith that the consortium will take necessary action to ensure as fair a test as possible.”