Nicky Morgan was right when she questioned the government's plans for new grammar schools: “We no longer live in a world where we need only the top 20% or 30% to be highly skilled,” she said. “We need everybody to have access to a knowledge-rich, excellent academic curriculum.”

It’s this point that should be at the heart of the education debate. Grammar schools were created with a vision of academic excellence for 25 per cent of children. Those children were destined for University while the other children would be trained for manual or technical work. But the schools outlasted this plan, and we have never formally redefined their purpose. We simply adjusted our reasons for liking them.

Now, more than 40 per cent of children progress to higher education, but there has been no review of the impact of grammar schools, which go on selecting 25 per cent of pupils, just as they’ve always done.

Where I live in Kent the grammar school system leads to enormous stress for parents who believe their child deserves a grammar school place. With spaces limited parents spend thousands on tutors, hoping to give their child an advantage, while avoiding the lower status schools. Many children miss out on grammars by just a percentage point or two. Bizarrely, given that we ought to make the most of the talents of all children, the system considers these ten year olds to be lacking any capacity for a rigorous grammar education.

Imagine your bright, academically-minded son or daughter, missing out on a grammar school place by the narrowest of margins. They get no benefit from the grammar system, they only get the problems – they have less choice of secondary schools, and they attend schools pitched at low achievers.

We should also not pretend that these other schools are comprehensives, which would ordinarily contain a balance of pupils of all abilities. If we believe schools with many able pupils give an advantage, we need to accept that the schools with few able children give a disadvantage. Non-selective schools in grammar areas are unable to offer the academic stretch of top set lessons, and usually offer sixth forms with a vocational focus.

Notice too how we don’t have a name for these schools. The term secondary modern is certainly not a popular one and for the most part we prefer not to talk about them at all. If we plan to expand selective education we need to acknowledge these schools exist. To dodge that, as I fear we are on course to do, the reality of grammar school expansion will be an overall decline in educational standards.

Some claim that the 11-plus makes education a meritocracy. But far from being an accurate appraisal of a child’s academic status and future ability, the 11-plus could more accurately be described as gauging parental involvement. Nor does it assess any of the attributes we might wish our children to have as they enter the world of work, such as problem solving, teamwork, leadership, not to mention their ability to work hard, or pick themselves up after a set back – qualities we all admire in adults, but for some reason not in children.

We would never look around our workplace and define a specific percentage of colleagues as ‘smarter’ than the rest, yet selective education suggests this is a concept that can work. Grammar schools offer an artificial divide and a troubling message: that academic ability is fixed at age ten for the few who can succeed. I prefer the message of a comprehensive meritocracy, suggesting effort at any secondary school can lead to academic success.

Grammar school advocates also claim selective schools increase parental choice, but the reality is that selective education removes the option of a comprehensive education, denying others that choice. If parents prefer academic schools then the very nature of selective education will disappoint many. Only a fixed percentage achieve their wish, the rest finding schools skewed towards the needs of lower ability pupils. Equal status schools, each capable of offering high quality academic provision, give parents much greater choice.

We should be proud that our education system has undergone massive improvement. Schools now offer a rigorous academic curriculum and regular tests to measure pupil progress. We no longer let lazy comprehensives get away with doing a bad job; we make all schools accountable for pupil’s results. This makes an eleven-plus unnecessary, especially as an indicator of a child’s ability.

If we wanted a policy for high achievers we could create a plan using current school testing and use Ofsted to monitor results. We might also use academic sixth form colleges for pupils with the best GCSE results. Five years’ schooling will show us the most academic pupils - an optional eleven-plus will always miss some, denying them their chance to succeed.

The country, our economy, and the future in general demand all pupils to have a rigorous education, considering the full range of skills employers’ value. As Nicky Morgan said, we should be preparing all of our children for a vastly different world of work to that which existed when the grammar system was established.

Many mixed ability secondary schools already achieve great results. We should be building on policies that are already working. Patchy grammar school provision is not an effective plan for high achieving pupils, and it endangers the great progress we’ve made with comprehensive education.

Joanne Bartley is a member of Bright Blue and campaign coordinator for Comprehensive Future