I have a lot of time for teachers who sign up to become moderators each year. I have no idea why anyone would put themselves through it and, sometimes, I wish they wouldn’t, but all thing’s considered, they are a good bunch of people. My own experience of moderation - in the confusing first round of post-levels writing judgements - was pretty much in line with what I’d heard always about moderation: a professional dialogue with a conscientious and expert practitioner.

Our whole assessment system relies on the contributions of these fine people. Unfortunately, that means that they, too, have become caught up in the current chaos. Last week, Ofqual was quite clear in pointing out the many failings of the moderation system that is used for key stage 2 writing. Ofqual’s report clearly states that it can’t make definitive judgements: it was based on only a very small sample of fewer than 20 local authorities. But the fact that the watchdog found so many discrepancies in such a small selection speaks for itself.

There are no surprises in the report for any of us who have even glanced at the moderation system and its flaws. The issues are familiar to us all.

For a start, there are problems with the training for moderators themselves. Setting aside the dreadful issues last year, when two-thirds of moderators failed the initial test, there were also problems because the initial training was so poor, and then the training offered by each local authority to its teams varied so much. None of that was helped by the fact that it was hard to get clear answers from the Standards and Testing Agency about any issues.

When it comes to the process in schools, firstly, the Ofqual report highlights the fact that some schools can pretty confidently predict when they will be moderated, and might also get up to four weeks’ notice of being selected, while other schools might get as little as 48 hours’. Then, when the moderation day comes around, you might find yourself with a single moderator or a pair or even a whole room of them. The scope for inconsistencies is clear.

Schools might muddy the waters themselves. Some will be open with moderators, sharing their exercise books from throughout the year - warts and all - to give a clear idea of what has been achieved; other schools, as Ofqual saw, will select a portfolio of finished pieces to be used for comparison. Hardly the fairest match. And, as the report says, some of that work may well have been “produced in a relatively less independent manner”.

Some moderators were seen to be asking about background details of each individual before considering their work, while others clearly interpreted some of the requirements in a way that might suggest “departure from the intended assessment standards, toward moderators’ personal beliefs”.

It’s laughable to think that all this can get us anywhere close to a robust and reliable system of comparable data. And that is before you take into account the 75 per cent of schools that don’t receive a moderation visit at all.

Unfortunately, it’s not Ofqual’s place to say that a system is completely broken: it can only offer advice to the secretary of state about the risks involved with assessments.

The risks here are clear, and yet here we are about to go into another cycle of the process. A new framework means that, once again, nobody is familiar with the expectations, and this time we have the bizarre notion of “particular weakness” to contend with. I rather suspect that the particular weakness here is within the system itself.

Michael Tidd is headteacher at Medmerry Primary School in West Sussex. He tweets as @MichaelT1979