Even as a boy I had grudging respect for the craft of teaching. The classroom a stage; the space physically claimed. The heightened, declamatory voice. Eyes that could melt, in an instant, from warm regard to iced contempt.

The ones I quietly loathed – and there were many of them about in my time – were the teachers who simply did not like children: odd, if you have chosen to spend four decades of your life dealing with them daily.

And the mystery of classroom order. I had one master who could not have kept control of the class with the 101st Airborne Division.

He shouted. He shrieked. Went beetroot-red, foamed at the mouth and belted with abandon, as we danced on our desks and laughed at him.

And then his senior colleague would materialise in the room. Like the shopkeeper in Mr Benn. A man who did not need to raise his voice. Looked us over with infinite scorn. The slightest curl of his eyebrow, the flaring of a nostril – and we were reduced to quivering silence.

The great teacher can spin, in a moment, from the Archangel Gabriel to Caligula, and the ambitious teacher wants a career trajectory that will win them more and more non-contact periods.

Mairi McAllan has been left in a difficult position by her predecessor 

Blocs in the day when they do not actually have to teach. Not spent – forfend the thought – chillaxing in the staffroom with The Guardian. Time they can devote to class preparation, marking homework, tweaking the curriculum or attending senior-management meetings.

The stuff they would otherwise have to do in the evenings or over the weekend, in their unpaid time and at the expense of relaxation and family life.

It’s a long career – you are expected to put in 40 years – and a draining one.

Teaching mixed-ability classes, from the biddable to the revolting, maintaining order, constantly engaged, having authority while keeping appropriate, if good-humoured, distance.

Given the generous holidays, days off are frowned upon. You might begrudgingly be allowed an afternoon for Granny’s funeral. Many do not, in the end, have enough resilience in the tank to complete their long course – and that’s before you start dealing with parents, many of whom no longer respect anyone’s professionalism or authority.

‘Ma Jimmy wiz swearin’ at me oan the stairheid the day – whit urr youse gonnae dae aboot it?’

All this is topical because, back in 2021, the Scottish Government promised all Scotland’s teachers a reduction in class-contact time: they enjoy the fewest no-contact periods in Europe and many are buckling.

But the SNP had not thought the policy through, how to deliver it and how much it would cost. As the end of the last Scottish parliamentary term came into view, Scottish teachers lost their patience and threatened to strike.

In an age when most mums and dads are in full-time employment, a general teachers’ strike is electoral death and Jenny Gilruth, Cabinet Secretary for Education, did a lot of fast talking.

Pledging more funding for local authorities and generally to ‘fully fund’ whatever the cost of more periods away from assorted Rodericks and Fionas would prove to be.

It was but kicking the can down the road and it is now a ticking bomb for her successor – Màiri McAllan – and it is fraught with difficulty.

It will be possible to grant more non-contact time to primary teachers from August next year – you just rope in classroom assistants for a spell – but despite promise of lightening of the load in high schools from 2029, it will be a difficult pledge to keep.

For one thing, there are fewer teachers in Scotland now than when the SNP assumed power in 2007. For another, there are growing problems in recruitment, especially in such vital subjects as English, maths, chemistry and modern languages.

And, in her rush to be loved, Jenny Gilruth forgot that in considerable swathes of Scotland we do not enjoy the typical local comprehensive, with 1,000 to 1,200 pupils, four or five feeder-primaries and rakes of depute head teachers and principal teachers.

In the likes of Tobermory, Ardnamurchan or Tarbert in Harris – all, I believe, very good and happy schools – we have much smaller operations where we do not, for instance, have a principal teacher of mathematics with half a dozen assistant teachers.

In rural and island local authorities there have been recruitment problems for many years. In some areas, trained primary teachers are now doubling up for classes in early secondary, or colleagues help with subjects in which they are not actually trained.

There are folk of the calibre to do this – a past headmaster of Jordanhill, Andrew Walker, is still revered for his ability to take a class in every subject save French – but it is scarcely ideal.

Addressing MSPs this week, Màiri McAllan declared work is still going on to figure out how much this policy is going to cost. And added, unnervingly, that one of the reasons for this is that we ‘might need to recruit more teachers’.

There is no conceivable way to increase teachers’ non-contact periods without employing more teachers and if, after months in the job, the Education Secretary is just foggily beginning to grasp that, then the SNP administration is more at sea than we thought.

And all this on a policy it committed to half a decade ago and which we were assured, time and again, was a matter of serious study over the last parliament.

Nor can John Swinney’s administration unilaterally change teachers’ terms and conditions. It will need the agreement of the Convention of Scottish Local Authorities, and the assent of unions like the Educational Institute of Scotland (EIS). Neither is a given, and they will need to find a lot more money down the back of the sofa when public finances are basically bust.

Bluntly, Jenny Gilruth’s pledge is undeliverable and, in a year or two, the bomb will finally go off in the most bitter teachers’ strike since 1974.

In an EIS ballot in March, 93 per cent supported ‘industrial action short of a strike’ – and 85 per cent an unambiguous strike – should the promise of 90 more non-contact minutes a week not be kept.

A far more menacing prospect than making wee Johnny stand behind the blackboard – my occasional experience during the Heath administration – as a colleague theatrically declaimed, ‘Oh, my, is that a bad boy you have there, Mrs Raeside?’

Others were more imaginative. I once had a teacher with a novel punishment exercise: offenders had to write out her name a hundred times.

It was Mrs Szczuka.