As more details of the government’s education reforms emerge, they look ever more ill-conceived and illogical. We already knew of the plans to lift the ban on new selective grammar schools, but Theresa May’s recent ‘Britain, the great meritocracy’ speech gave concrete evidence of her intent.

The old arguments were reeled off, but her overall message was how ‘things would be different’ this time. She insisted that there will be no return to the old system, which provided a tentative leg-up for some, and an almighty stomp-down for the rest (a system, by the way, shut down in the 1960s because it was failing, and which remained quiet under every successive government – even Thatcher’s).

What are the new ‘solutions’ that May suggests? She claims that selective schools will raise outcomes for all pupils in every part of the system. A proportion of kids from lower income households could be given places, and selective schools could be asked to sponsor a non-selective counterpart. There could also be more flexibility in moving between schools – perhaps at 14 or 16, not just at 11.

Those propositions are like putting a plaster on a chainsaw wound. The government is at pains to insist that the fear of a return to the binary system is unfounded: “There will be no return to secondary moderns”, the Prime Minister said. Yet the glaring truth is that a selective system, by its very nature, is binary. It’s a thumb-up or thumb-down, at age 11, and that’s morally wrong. It consigns the vast majority, probably 75 per cent or more, of children to schools that will be worse than current comprehensives, stifling their chances while they watch a select few squeeze all the benefits from an unfair system.

Besides the moral argument, the hard evidence against grammar schools is crushing, and could fill scores of articles. Given May’s government’s attachment to the vague idea of meritocracy, a poignant argument is that the beneficiaries from this policy will almost certainly be the wealthy middle classes.

The basic arguments simply do not go away: free school meals are almost 10 per cent less common at grammars; poorer children consistently do worse academically in local authorities with grammars (in Kent, where selection remains, 27 per cent of kids on free school meals get five good GCSEs, compared with 45 per cent in London); tutoring for the 11-plus, to those who can afford it, provides a massive advantage. For poorer students, the game’s rigged: the pass rate for those on free school meals is a paltry one-eighth of the average.

May’s recent suggested solutions will do nothing to alter these hard realities, or change the fact that a selective education system is iniquitous at its core. The case against grammar schools as part of a fair society is open and shut.

But what should be done instead? The answer is to concentrate not on structure, but resources – as every teacher, educational expert, and most politicians (May’s even managed to unite Labour on this one) know.

Peter Hyman, a key New Labour strategist, lays out the problem in his brilliant book, 1 out of 10, where he tells of his experience quitting politics in 2003 to become a teaching assistant at a failing comprehensive school in London. There he discovered what really makes a difference to kids’ life chances: not top-down structural change but the quality of teaching, and making resources available to schools to do what they, as experts on the front line, think is best.

Even former Education Secretary Nicky Morgan agrees. This new policy, she said (possibly in an effort to ensure her own legacy), is a “distraction from crucial reforms to raise standards”. The chair of the Social Mobility and Child Poverty Commission, Alan Milburn, stresses that teacher quality and parenting are the most important issues, not the system’s structure. He recommends much more considered policies, like giving teachers financial incentives and help into the local housing market in areas that are in desperate need of good staff, ensuring excellence across the country. The £50 million that the Prime Minister has pledged to the grammar scheme would be much better spent on raising standards in ways like this, which will truly help the brightest children realise their potential and go on to achieve great things.

Yet this won’t happen. If politicians worry about one thing, it’s their legacy, leading them to favour bold overhauls over thoughtful policy: think ‘May’s grammar reforms’, not ‘Morgan's tweakings’. One of the most pertinent messages from Hyman’s book is about the shadow that falls between the politician’s idea and the reality of its delivery. Effective policy, he (now the headteacher of a London school) writes, is “about the combination of often small things that build over time”; it’s about “the grind, not just the grand”.

However, this won’t be Theresa May’s way. Her ideological drive for more grammars shows that her reputation as a safe pair of hands is colossally overstated. In her first few weeks as Prime Minister, she has tarnished the idea of her proclaimed fairer society with a rash and clouded call for a return to educational segregation. It took only a couple of months for her to choose exclusion and division over cohesion and unity. The mask may have cracked already.