Peter Walker, formerly of the Abbey school at Faversham, who brought in RDT despite much headshaking, has jetted to the US to advise their drug zsar and boomeranged back to be appointed an “ambassador” for it here. Headlines excitedly talk of government rolling out the whole shebang as fast as possible. (I always love that talk of rolling out. As if some kind of foam-backed carpet could be laid, at speed, over all the awkward bumps and ridges of school life.) In favour are several things. It gives a clear signal that even weekend drug use is neither permissible nor unavoidable. It presents a chance of catching marginal users at an early stage. The more expensive tests - saliva, hair clippings - pick up a wide range of drugs, not just cannabis.

Most vitally, RDT gives the children a weapon against peer pressure - “Sorry, I’m cool, but my school does them rando-tests, know wha’ I mean?”.

Arguments against are equally worth hearing. It would, opponents say, destroy trust between staff and pupils, creating an atmosphere closer to a prison than a learning community. It would be embarrassing and intrusive, especially if they chose the cheapest test, which is urine, and were punctilious about supervising its provision. It might infringe civil rights. It would, above all, encourage children to try alternative thrills which their school’s chosen test did not pick up - heroin, perhaps, or shoe polish, or some hideous life-threatening cocktail of Tipp-Ex and Ritalin (“white-out” which can kill you).

Another counter argument is the expense: the more discreet and broad spectrum the tests, the more they cost, and most of this money would be wasted on random testing of pupils who take nothing stronger than Marmite soldiers, while the real potheads order stuff called Chem-Hide and No-Tox off the internet to fool the system.

There’ll be plenty of argument. Good. But I just want to throw in one fact, because a year ago I visited Peter Walker’s school at Faversham, pioneer of random testing. I was more interested in his innovative behaviour management systems. This school - with a particularly challenging intake and within a grammar school county - famously upped its GCSE results and discipline over the period of RDT. This fact will be taken by government enthusiasts as proof that it is a damn good idea, a magic bullet, and that if you could only scare the little bleeders off drugs they would all learn to read and count, stop wearing hoodies and make Britain great again.

But the point about Mr Walker’s school was that he didn’t drop the testing regime on them from a great height, in isolation. Oh no. He had looked at the social and behavioural problems that were rife (though not universal) among the families he served, and had concentrated hard on alleviating them as far as any school ever can.

He hired 70 non-teaching student guidance counsellors: sensible kind women were in evidence everywhere, chatting, befriending, soothing and encouraging, like good mothers. He also set up a system whereby the first sign of disruption in class could be signalled by intranet, and before the noise level rose, the culprit would have been removed to a pleasant room with sofas and a kind adult to have the problem discussed. “To see if you’re being bad or just sad. S’a different thing,” observed one child sagely. Usually they were back in class, less sad, in a short time. For plain badness there was an internal exclusion room with work and harder chairs.

But the point is that pastorally this school was dense and concentrated: it had more guidance counsellors than teachers. And, in its particular circumstances, it worked rather well. If a perverse admissions structure and a difficult catchment area throw you a high proportion of children with problems, ready to pass them on with interest to others, then you need to re-invent the concept of what a school is for.

That is what Peter Walker did. He tackled the whole child; the whole problem. He didn’t just wake up one morning and say “Right, you little rats, drug tests for you!”. Harry Potter’s Dumbledore didn’t transform performance and behaviour with a magic chemical wand. Random drugs testing was part of a wide, thoughtful and laborious process. Most of the staff agreed to be tested, too.

I just wanted to make that point, now. In case anyone decides RDT is a shortcut.