The union was speaking just after a YouGov poll in the Times Educational Supplement revealed that only 38% of the public back new grammar schools, though two-thirds would send their child to one if they passed the entrance test.
The poll came on the back of a widely reported story in the Sunday Telegraph earlier this month, which suggested that prime minister Theresa May, herself grammar school educated, was this autumn set to announce plans for the opening of new grammar schools.
The TES speculated that one person influencing a push for more selective state-funded school – with places allocated for children from low-income families – is Nick Timothy, who was Theresa May’s leadership campaign manager.
In July Timothy left his role as director of the New Schools Network, a charity aiming improving education through free schools, to work for the new Conservative prime minister as joint chief of staff. He had previously worked for May for five years as a policy adviser.
Prospect national secretary Philippa Childs said: “It would be worrying if free schools were used as the back door through which to open new grammar schools.
“But whatever mechanism is used, wherever a selective school opens in an area, you also have to consider the knock-on effect on all the other secondary schools in that area, and on the children who have to attend those schools.
“Our members are of the view that in a society which has become markedly less equal over the years reintroducing grammar schools would be a significant backward step.”
Stroud MP Neil Carmichael, the Conservative chair of the Commons education select committee, responded to the Sunday Telegraph story by saying he would fight any move to allow new grammar schools to open in England.
In an interview on BBC Radio Four he said: “We have serious issues about social mobility, in particular white working-class young people, and I don't think that having more grammar schools is going to help them.
“I think that the creaming off of the best is actually detrimental to the interests of the most.”
Labour’s shadow education secretary Angela Rayner has highlighted research by the Institute for Fiscal Studies http://www.ifs.org.uk/publications/6936. One of its findings is that even among high achievers, children living in less affluent neighbourhoods, or relying on free school meals (used as an economic indicator of social deprivation) are far less likely to attend a grammar school than those from wealthier families.
The Sutton Trust chair Sir Peter Lampl said that grammar schools were not the solution. “Instead there should be a national drive to improve education for the highly able in comprehensives.”
A Sutton Trust factsheet shows, among other things, that in 2013 fewer than 3% of entrants to grammar schools were entitled to free school meals, whereas almost 13% of entrants come from outside the state sector.