Last week, Ofsted finally admitted defeat.

It’s been a long time coming, but it came. It happened quietly, so quietly that most people didn’t notice. The entire Ofsted schtick collapsed, and only smoke and mirrors can now continue to persuade anyone that the house of cards still stands.

For months now, we’ve known that a vast number of schools haven’t been inspected for a decade or more. They were judged "outstanding" back then, and are still judged as "outstanding" today. Nevermind that the entire national curriculum has been rewritten in that time, that pupil premium has been introduced as services around schools have been decimated, that a funding squeeze affects us all, that professional and CPD standards have been altered, that teacher training has been revolutionised, or indeed that the Ofsted framework itself is on its third incarnation since.

The data the schools provide is stable and no safeguarding concerns have been raised, so that’s that. "Outstanding."

Push Ofsted a little, and it will blame a lack of resources. It simply can’t be everywhere all the time. Fair enough, you’d think, but what we learned this week – thanks to none other than Amanda Spielman herself – is that at the other end of the performance spectrum are 500 schools that the inspectorate has identified as "stuck".

Ofsted doesn't support school improvement

Five hundred schools have been in a category of "requires Improvement" or "inadequate" since 2005 and have never escaped. Let that sink in. Any notion that Ofsted supports school improvement is entirely belied by this fact. I know. I worked in one until my health was robbed by the experience.

Where are the inspectors that ought to be inspecting the uninspected so-called "outstanding" schools? They are entirely occupied informing, reforming, deforming, pro-forming, conforming, uniforming and transforming these 500 schools.

To absolutely no avail.

The only positive correlation between their work and any school measurement data is with mental ill-health, and the recruitment and retention collapse. The former isn’t considered by the Big O (I’m given to understand data is too unreliable), but check these schools’ reports and I’m certain you’ll find recruitment mentioned with depressing regularity.

Just as depressing in my experience is the lack of any mention of poor retention. Why? It is assumed a positive. The school gets rid of inadequate teachers, demonstrating its capacity to improve. If only they could recruit better ones! But they can’t, precisely because they’re in an "inadequate" category. So they burn out the ones they have, until they discover they can go shopping abroad for new blood. Northern Ireland, with its over-supply of newly qualified teachers, is particularly fertile ground. Then rinse and repeat. Churn and burn.

Imagine finding out all that suffering is pointless.

If you’re not empathising yet, what if I told you it’s partly your fault?

You see, there is no school mobility within the judgmental framework Ofsted has deployed. Somewhere in a Whitehall drawer is a bell curve graph of schools that respond to external pressure. At either end of that bell curve are hundreds of schools for which Ofsted is of no use whatever. Those deemed "outstanding" don’t get demoted, and those deemed "inadequate" don’t get promoted.

If this is true for those schools, I’m afraid to say that no matter how proud you are of your Ofsted "good" badge, no matter how swanky the banner on your school gate displaying it, it is also true for you. It is an arbitrary game with arbitrary rules that measure nothing but your compliance to political whim and the relative privilege of your school’s catchment.

Your banner and your badge? They validate the whole thing.

Yes, the entire culture of school competition is a scam. More than that, the entire academisation policy falls flat on its face with Spielman’s revelation. Though supposedly primed for forced academisation, the process has done nothing for 500 schools. Not a bean. I’d be interested to know how much has been spent on brokering and rebrokering them or building free schools next door and leaving the so-called stuck schools to fester. Scandalous amounts, I’d wager.

That’s the simple truth we are faced with. Ofsted has come unstuck and the academies policy with it. No hastily erected scaffolding bedecked with “This is a ‘good’ school” banners should convince you otherwise. No talk of a new framework should distract you from it. When Lehman Brothers crashed, the building was still there. Inside were grandiose and ambitious plans for the future. Outside were many who had invested much on the basis of its reputation. Yet, we live in a post-Lehman Brothers world.

Despite the damage done to me by six years working in an "inadequate" category, I’ve remained supportive of Ofsted. I’ve been critical. Anyone who cares to read my previous articles will see that, but I thoroughly believe that having robust accountability is a necessary element of professionalism and that every teacher deserves to be respected as a professional.

Ofsted has to do both or be replaced, and this is the last-chance saloon.

The only way to secure the swift and sustainable rebuilding of Ofsted is to dispose of categories altogether. The practice is perfidious as well as demonstrably useless.

The new framework should be premised on this, or it will continue to fail education, no matter how right it is. Let me be clear, if anything has the potential to unstick these stuck schools and see the complacent ones and exam factories at the other end come unstuck, it is this new framework. But the reports that result from it must not negate themselves by giving schools a grade as a proxy for reading them. The curriculum is the substance of education and it is too important for that.

• Make reports formative. Identify strengths and areas for improvements.
• Before leaving the school, agree on a date for returning based on the perceived urgency of the improvements needed.
• Spend the time between these dates brokering support from the community and other schools, instead of leaving leadership teams to swim in the shark-infested waters of school improvement consultancy.
• Take some ownership of the results.

It’s not rocket science, for Pete’s sake. It’s exactly what’s expected of us.

It’s good education.

JL Dutaut is a teacher of politics and citizenship and co-editor of Flip the System UK: a teachers’ manifesto, published by Routledge