The Conservative government should do more with existing grammar schools before extending the system across England and Wales, education charity Sutton Trust said on Monday (27 March).

Chief executive Dr Lee Elliot Major told IBTimes UK that the current number of children from poor backgrounds getting into the academically-rigorous institutions is "extremely low", with fewer than 3% of entrants entitled to free school meals.

"There's very little evidence that they improve social mobility," he said. "The main reason we would say that is, while they might do wonderful things for children that get into those schools, what all our research and other's research has shown is that the numbers of children from poor backgrounds getting into grammars is extremely low."

Major added: "You would have to do a lot more with existing grammars before thinking about expanding them more...[otherwise] you are just going to create more schools for the middle classes.

The Sutton Trust boss, who stressed that the charity takes a practical rather than ideological position on the issue, suggested the government and the current grammar schools could work more on outreach with primary schools and "maybe think" about lowering acceptance grades for pupils from poorer backgrounds.

Chancellor Philip Hammond promised £320m ($402m) of funding in his Spring Budget to create 140 new free schools, which are expected to turn into grammars. There were 163 grammars in England in 2012, compared to 3,000 state schools at the time.

Theresa May has controversially promised to end the 1998 ban on creating new grammar school. "The truth is that we already have selection in our school system – and it's selection by house price, selection by wealth. That is simply unfair," she said last September.

Nick Timothy, one of May's closest aides and a former grammar school boy, is reportedly a driving force behind the reforms. But the Conservative premier faces opposition on her own benches with the move. Former Education Secretary Nicky Morgan has opposed the selective schools.

"I do worry that a return to selection risks undermining the progress that we have seen over the course of the last decades in our schools by throwing something else into the debate," she reportedly told the Social Market Foundation think tank in 2016.