The dice is loaded against children from poorer backgrounds when it comes to grammar schools, according to a new report.
A study of data from Kent found that around a quarter of all students went to a grammar school in 2016, but children eligible for free school meals (FSM) were much less likely to pass, or even sit, the 11-plus.
Just 12% of FSM-eligible students passed the test compared to 30% of more-advantaged pupils, the Press Association reported.
Children from less affluent backgrounds also scored particularly poorly in the reasoning element of the test compared with others.
Lead author and Education Datalab director Rebecca Allen said the chances of gaining a grammar school place were like “rolling a loaded dice”.
She explained: “If the 11-plus is a dice, then the reasoning component contributes to the dice being loaded against disadvantaged children.”
Kent state primary schools were explicitly asked not to prepare their pupils for the 11-plus, suggesting only those whose parents help them practise, who receive private coaching or attend private schools will gain familiarity in this area.
Allowing state primary schools in Kent to provide 10 hours of practice on reasoning-style questions to all students could help increase the proportion of children from less affluent backgrounds entering grammars, the report said.
The research looked at data from pupils who sat the 11-plus in September 2015 for entry to grammar school in September 2016.
The data was obtained under the Freedom of Information Act by the Kent Education Network, a group opposed to selective education.
If the Conservatives stay in power after the June 8 snap election, Prime Minister Theresa May will have the opportunity to roll out her controversial flagship policy of more grammar schools for England.
She has said the policy will help to create a place at a good school for every child and argued that many children’s school choices are determined by where they live or their parents’ wealth.
But opponents believe it will entrench social division, with National Union of Teachers (NUT) general secretary Kevin Courtney saying there was “no appetite for this programme”.
Currently grammar schools only exist in parts of the country, including in Kent and Buckinghamshire, with a ban on new grammars introduced by Labour in 1997.
Kent County Council told the Press Association that social mobility in eduction is one of its main priorities.