When Amanda Spielman, our soon-to-be chief inspector of schools (HMCI), was questioned by the Education Select Committee in June, she said she wanted to have discussions about abolishing Ofsted’s “outstanding” grade as she was “quite uncomfortable about some of the effects you see it having in the system”.

Ofsted is a regulator and an inspectorate. Its remit in identifying and enforcing a clearly defined minimum standard of education is not disputed. Parents specifically, and the taxpayer more broadly, need to be sure that the quality of individual state schools is good enough. Heads and governors welcome accountability and transparency, and understand the reassurance that it provides for parents.

What is disputed is why Ofsted needs to spend any time, energy and money at all in defining, assessing and judging the degree beyond which any school is considered to be good enough. Spielman has correctly picked up that the existence of the grade “outstanding” is not only unnecessary, but damaging.

When two exceptional headteachers said to me recently that going from “outstanding” to “good” was the best thing that ever happened to their schools, you know the system is in need of an overhaul.

The Ofsted grading system is seductive. Distilling schools down to a descriptor of a single phrase, with an accompanying number, makes it easily digestible for interested parties. But therein lies its central weakness - inherently complex organisations that are all about working with human beings cannot, with any meaningful accuracy, be summed up in a single word. (Note that the Care Quality Commission and Her Majesty’s Inspectorate of Constabulary have adopted Ofsted’s grade descriptors wholesale for their inspections of hospitals and police forces, respectively.)

A brilliant former governor at our school understood this concept perfectly well: “Ofsted say we’re a ‘good’ school. Well, what do we do that is exceptional and what do we do that is rubbish?”

No school judged as “good” is good at everything it does. Indeed, schools that do not offer an acceptable standard of education and are judged “inadequate” will still be doing things that are very effective or, perhaps, brilliant. This is lost in the summative judgement.

If Spielman were feeling bullish, I would encourage her to review the entire system of grading and seriously consider the removal of an overall judgement for schools. Failing that, I’d settle for the removal of the “outstanding” grade. Here are my reasons.

1. The playing field is not level

So says Ofsted itself. TES reported in November last year that Robert Pike, Ofsted’s chief statistician, said that it is “harder” for schools with lower-ability intakes to gain “good” or “outstanding” judgements from the inspectorate. Pike also stated that it is “probably easier” for “schools with advantaged intakes” to be graded as “good” or “outstanding”. Removal of the top grade would help, but not completely solve, this deep-seated problem. Perhaps Progress 8 will go some way to helping secondary schools in this regard but, in any case, this glaring inequity - admitted by the inspectorate itself - must be addressed without delay.

2. Some children put a school’s rating at risk

Given the above point, it immediately follows that a school’s chances of being judged “outstanding” are reduced the more children they have on their roll who are of “lower ability”. This group includes those with learning difficulties and many children with special educational needs and disabilities. If attaining “outstanding” status, or a fear of losing it, has become the goal in itself (I have seen it on school development plans) then you can see how, as the children’s commissioner found in 2014, some schools say to parents that “it might be best if you looked elsewhere”.

3. It limits the supply of teaching schools

Schools can only apply to be designated as teaching schools if they hold Ofsted’s top grade. “Good” schools are not yet deemed of sufficient quality to be in the running to support other schools. The same is true for headteachers who wish to be national leaders of education (NLEs). Although the Ofsted framework does not judge individuals, Department for Education guidance on NLE application criteria states that you must “be judged an outstanding serving headteacher” to apply. I’m sure they mean that the school the headteacher works in must have a current outstanding judgement for leadership and management, but it perpetuates the fact that a school’s Ofsted grade instantly attaches itself to the headteacher.

The headteacher of a “good” school is, therefore, a good leader - no better, no worse. There are headteachers of “good” schools packed with the “low ability” kids who, along with their teams, are doing life-changing work and they should be out there as NLEs.

4. It doesn’t help with headteacher recruitment

Recruitment of teachers generally is difficult. The market is no better for leaders, with a sizeable proportion of vacancies having to be readvertised. Candidates consider carefully the context of the schools they look to apply to. Schools holding the top grade can be less appealing, as dips in results can lead to headteachers losing their jobs. In addition, newly arrived leaders in “outstanding” schools can face tough audiences when identifying aspects of the school’s provision that, to use the vernacular, “require improvement”.

5. It can narrow priorities

In the rush to attain the top grade, things that do not appear in the “outstanding” grade descriptors can be postponed or discounted altogether. I wonder how many headteachers have a performance management target that their school should be judged “outstanding” at its next inspection? I did once.

6. Abolishing ‘outstanding’ is a quick win

This should not be underestimated. Given the fragile and, at times, fractious, nature of the relationship between the inspectorate and the profession, removal of the “outstanding” grade would release the pressure valve and would be a message that HMCI is not seeking a dust-up with the profession for the hell of it.

7. Banners

I have a visceral dislike of the banners draped outside schools displaying their latest Ofsted grade, but I understand the reasons why they are there. When my school’s Ofsted judgement went from “outstanding” to “requires improvement”, our reputation took a big hit. Just 15 months later, we were free of that millstone, but there’s a satellite delay while the reputation heals itself and word gets around.

I understand why heads want to get the message out there, but banners are a blight and removal of the “outstanding” grade would, I hope, reduce their prevalence.

Jarlath O’Brien is headteacher of Carwarden House Community School in Camberley, and author of Don’t Send Him in Tomorrow