There are some ideas in education that refuse to die. That zombie statistic about children only being able to focus for a handful of minutes; the random myth about trainees not being allowed to teach PE; the mad idea that all children’s attainment can be neatly packaged into three groups.

This week, it’s the turn of no-notice inspection to rear its head once again. Long gone are the days of having weeks, or months, of notice about the forthcoming visit, but the idea that inspections can occur with virtually no warning has long appealed to chief inspectors, and it seems it appeals to parents, too.

The thinking is pretty obvious: who knows what steps schools might take in the current 19-hour window between the initial phone call and the arrival of the inspectors at the door?

The presumption is that some schools hide their worst pupils (or maybe teachers); that others pull in resources and support that aren’t normally available. Inspectors just don’t see the school as it really is.

It’s tempting, too, to make comparisons to other sectors. Restaurants don’t get called the day before a hygiene inspection, and given time to finally throw away the rotting meat and sweep up the rat droppings. Surely schools should be treated in a similar way?

Confusion about the role of Ofsted

It all rather highlights the confusion about what Ofsted is for. I suspect parents are broadly supportive of the idea - particularly in secondary schools - because they fear that behaviour issues and unruly pupils can be hidden if schools are warned of their impending visitors. If the purpose of Ofsted is to check that schools are keeping good order and that badly behaved pupils are being dealt with, then maybe that’s the case.

The problem there is that parents often have much more strident views about what should be done about misbehaviour than do schools or the inspectorate. Perhaps those parents who want no-notice inspections would be disappointed when they discovered that inspectors agreed with schools that things are not quite that simple.

In any case, if reports are to be believed, the proposed 150-minute warning period is less about checking on behaviour, and more about getting into schools to plan the inspection. Last week’s report even points out that it’s not a reduction in the notice period, and the inspection would only formally begin on the second day. Would inspectors have to pretend they hadn’t seen any poor behaviour in the first afternoon?

Of course, inspection is about far more than behaviour: things which are perhaps of less interest to parents. I very much doubt that there is a large body of parents who think no-notice inspection is necessary to ensure that sports premium funds are being well spent and evaluated or that school websites correctly list the name of the person who answers the telephone.

Particularly as inspections have got shorter, and inspectors fewer, the demands of an inspection are much more about probing leaders’ knowledge of their schools and ascertaining their capacity to improve them. None of that will be made clearer by a shorter notice period.

Having been inspected myself just this month, I know that the afternoon notice period I had was largely spent sorting out practicalities: who would introduce the nativity performances if I was needed by the inspector? Which intervention groups would need to be moved to make room for the inspector to work? Even sending out the parent and staff surveys don’t happen by magic.

Of course, if you really want to know what happens on an ordinary day in a school, inspectors only need do one thing: ask pupils, “Is it normally like this here?” They’ll soon tell you what it’s really like.

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