Politicians love to find scapegoats. Single mothers, communists, the media, trade unions, bankers, hoodies, ethnic and religious minorities - all these have, at various times in history, been identified as the enemy within.

Politicians cannot admit error or inadequacy. If things go wrong, they have to blame someone else.

Take James Callaghan. He became prime minister in 1976, with inflation at 16 per cent, interest rates 15 per cent, unemployment 1.25 million and rising, economic growth well under 2 per cent. It was a miserable autumn during which it rained almost continuously. Callaghan’s troubles culminated in September 1976 when the Government had to seek a loan from the International Monetary Fund, conditional on sharp public-spending cuts.

The usual suspects were unavailable. Bankers, Labour’s traditional scapegoat, couldn’t be blamed. Callaghan needed their money. Nor could he blame the unions. Labour needed them even more than usual because its “social contract” with the unions, intended to keep pay rises under control, provided almost the only hope that Britain could dig itself out of a very deep hole.

So Callaghan hit on the teachers. In a speech at Ruskin College, Oxford, in October, he warned that the teaching profession was losing the confidence of “parents and industry” and was “laying up trouble for itself”.

He had decisively identified a new national scapegoat which, like the poor creature originally chosen to atone for Jewish sins during Yom Kippur, has been driven deeper and deeper into the wilderness ever since. It was possibly the only lasting contribution to our national life that Callaghan made during his brief premiership. Nobody could remember the last time a prime minister had said anything substantial about education. And even Margaret Thatcher, education secretary during the Tory government of 1970-4, had trained her hostility on the National Union of Teachers, rather than on teachers generally.

Callaghan turned “teachers” into “the teachers”, a subtle but important linguistic distinction with which any ethnic-minority is familiar.

What brought teachers further into the firing line was the decline of two other prominent scapegoats which had served politicians well for most of the 20th century. After the fall of the Berlin Wall and the collapse of the Soviet Union, the red menace was sadly diminished. The same happened to the unions after the Tory legislation of the early 1980s.

Teachers have proved ideal scapegoats. They are numerous enough to be credible, and they have ample opportunities to subvert the young, a very useful attribute in any scapegoat. They can be blamed for more or less anything: the nation’s social, spiritual or physical shortcomings as well as its economic ones. If something is wrong, but it’s not actually on the school curriculum, teachers can still be blamed for neglecting to teach it.

Unlike bankers and unions, they are conveniently adaptable for any political purpose. Just as Jews were held responsible for both communism and capitalism, so teachers can be blamed for both upholding the status quo and subverting it. Sometimes they can be blamed for the same thing for opposite reasons. All politicians agree teachers are responsible for underage sex and unwanted pregnancies. Half of them say it’s because there’s too much sex education, the other half say there’s too little.

You may wonder why, with some 400,000 teachers at large - to say nothing of their families, friends, and non-teaching colleagues - politicians don’t worry about their votes. Unfortunately, teachers are too evenly scattered across the country to create effective political pressure. This makes them better scapegoats than the unions ever were, because some constituencies had heavy concentrations of, say, miners or dockers. It also makes them better scapegoats than Muslims because Muslims, too, tend to cluster in particular areas. On the other hand, though the best scapegoats can live anywhere, they should meet regularly in locations largely inaccessible to the wider public. Jews met in synagogues, bankers in Zurich, trade unionists in smoke-filled rooms. Teachers meet in staffrooms, lodged in almost everyone’s psyche from childhood as places of mystery and possibly unmentionable practices.

I see no early prospect of teachers escaping their role as political scapegoats. They will just have to grin and bear it. I advise borrowing from the character in Katherine Anne Porter’s novel, Ship of Fools, who has to listen to someone boring on about the Jews. Hear out a politician (or anyone else) blaming “the teachers” for whatever it is. Then say: “Yes, it’s the teachers and the bicyclists.” They will then say: “Why the bicyclists?” And you reply: “Why the teachers?”