Food safety inspectors can march into restaurant kitchens without warning, all the better to spot the cockroaches scuttling past the fridge. So what is wrong with Ofsted's plans for surprise inspections of schools?
If inspectors only visited to check that pupils were safe and not slipping into puddles of acid in the chemistry department, perhaps no-notice visits would be useful. But the two types of inspectors have very different sets of expectations.
Food safety inspectors do not demand that restaurant owners give them paperwork to show the quality of their meals exceeded the expectations of 80 per cent of their diners. They do not stand in the kitchens muttering that the cuisine is lacking in invention, when the chefs sometimes have to cook baked beans on toast because it is on a nationally prescribed menu.
Above all, if the inspectors think the food is not as good as at competing establishments - even if it is perfectly safe - they do not threaten to close the restaurant, then write to all its customers telling them the cooking is below average.
The current Ofsted system is a great improvement on the previous longer notice inspections. Then, the weeks before a visit could be a misery for staff if their heads panicked and thought they had time to restructure the entire curriculum.
Two days' warning is not enough time for such changes, but sufficient to ensure pupils are not all out on trips and that teachers have a fair chance to show their potential.
No-notice inspections would put schools on a permanent state of alert, encouraging weak managers who lack confidence in their staff (or themselves) to get even more bogged down in bureaucracy. That is no way to run an effective school.
Even the inspectors think no-notice visits are impractical (see page 9). The danger is they may also treat inspections less seriously if they regard them merely as a random snapshot. Inspectors already appear too inclined to place more weight on the evidence of a school's past test results than what they actually witness in the classroom. No one who read the damning report given to New Manton Primary in Worksop (page 14), for example, would have predicted its startling improvement this year.
Surpise and fear should play no part in school inspections. The chief inspector, Christine Gilbert, should think again.