The row over how Ofsted labels schools reveals the power of some very ordinary-sounding words.

Chief Inspector Wilshaw, who sounds like a Ruth Rendell character but is in fact in charge of scaring teachers, has said his Ofsted team should no longer judge any school to be satisfactory. He says it is “not good enough” that 3,000 schools have been satisfactory for two inspections in a row. These schools are “coasting”, he says, and “not providing an acceptable standard of education”.

So how can satisfactory be neither good enough nor acceptable? My dictionary says it’s both. In fact it’s better than that. If you satisfy an expectation, you meet that expectation fully – job done. If you satisfy your doubters, you convince them – end of. If you demand satisfaction you are not easily pleased, no sir. If your hunger is satisfied – well, you get the idea.

But Ofsted aren’t using satisfactory like this. They’re using it as one point on a four-point scale: inadequate, satisfactory, good, and outstanding. Here, satisfactory is better than some, but not as good as others. However, the excellent word research tool Sketch Engine shows that the verbs people most associate with satisfactory are deem, prove and judge. Put satisfactory after any of those and you see how people often think of the word as an ‘absolute’ – something’s either satisfactory or it isn’t. It’s not a point on a scale.

At the same time, the adverb most associated with satisfactory is reasonably. That very much puts satisfactory back on a sliding scale, interchangeable with could do better. If that association resonates strongly with you, you’re not going to be very satisfied with a satisfactory school.

DCI Wilshaw is not satisfied with satisfactory either. Nor is the Prime Minister. In an Orwellian flourish, Mr Cameron has declared, “I don’t want the word ‘satisfactory’ to exist in our education system. ‘Just good enough’ is frankly not good enough.”

The label these gentlemen prefer is requires improvement. Sketch Engine tells me that improvement is most commonly associated with continuous, significant, marked, dramatic and substantial. All nice positive stuff. And as part of a scale of grades that schools can achieve it makes sense. But as a standalone phrase – ‘your school requires improvement’ – well, you can see why the word the teachers’ unions are using is ‘insulting’.