Since education generally comprises both principle and practice, there is an utterly apt irony at the core of the secondary teachers' dispute. Most reasonable commentators accept that, in principle, the ASTI has a strong case. However, most reasonable commentators also accept that, in practice, by rejecting the terms of the Programme for Prosperity and Fairness (PPF), the union has backed itself into a cul-de-sac which not only undermines its goal but, arguably, makes it unachievable. Principle and practice - supposed equal and complementary aspects of education - are therefore irreconcilable.

Two weeks ago, Fintan O'Toole argued that because of its tactics, the ASTI had "turned into a white-collar version of the ILDA - a breakaway union outside the loop and left to its own devices". In terms of realpolitik - politics based on material realities rather than on morals or ideals - this is undeniably true. In principle, however, the ASTI sees the "loop" as a noose and in both principle and practice, the union has a strong point. The PPF, though it has obvious merits, ought not be treated as sacred. It too must be open to examination on more than just its own terms, which are, above all, the terms of business.

Teachers resent the business types and managerial 'experts' whose rising power has displaced their own. A letter published in The Irish Times last Friday said as much and more: "Teachers are afraid of an ignorant, distorting system of evaluation derived from business-oriented strategic management thinking . . . The wise men of the benchmarking bench have no knowledge of education and do not understand why the management of a school should be any different from the management of a factory."

This is as undeniably true as the pragmatic reality outlined by Fintan O'Toole. In principle, performance evaluation ought not unduly upset teachers. In practice, however, they have good reason to be concerned.

Performance evaluators themselves, they know that many in the business community believe that academic institutions often lack relevance.

Business - and it's only fair that it should - prizes realism, initiative and efficiency as the pillars of economic progress. In such a scheme of priorities, business characteristically treats academic learning as, ultimately, a concern of dilettantes destined to be underlings.

An anecdote told about Denis O'Brien, a legitimate hero of the business classes, recalls how he couldn't understand why a university classmate might read a book "not on the course". He could see no point in such timewasting. Well, he's gone on to acquire hundreds of millions of pounds, which makes him an exemplar of a certain kind of project. The same criteria applied to evaluating teachers' performance - even given the grotesque points scramble - would be disastrous.

Writing in this space last week, former Minister for Education Gemma Hussey referred to school pupils as "consumers". That is the language of commerce, appropriate in a commercial context but inappropriately appropriated when it is applied to an activity such as teaching, which is concerned with more human and less tangible interactions than simple supply and consumption.

So, although the ASTI is tactically and practically wrongheaded, its view from the cul-de-sac points up principles which ought to concern us all. For a start, the reality of the PPF (in practice, whatever about in principle) is that its deals are essentially those of "economic partners" and not simply, as the political power-brokers pretend and the media supinely accepts, of "social partners". Basically, the PPF is a bargaining process in which the unions castrate themselves for a price which satisfies most but leaves the buyers - employers - sufficient room to make profits which continue to widen the wealth gap, obscenely in some cases. In realpolitik terms, it may be the best the unions can do but even if it is, the reasons why are worth examining.

If such reasons are considered academic (or even, in populist businessese "merely academic") that doesn't automatically mean they are irrelevant. In fact, if such reasons are seen as academic - given that we're talking about teachers - that makes them especially relevant. All academic institutions, most notably, of course, third-level ones, are being colonised by business and business-thinking. The result is that chairs and research programmes are being sponsored by private capital, and it's idiotically naive not to suspect many of the agendas presenting themselves as largesse.

Second-level schools should fear that they too may be consumed (the word seems genuinely appropriate in this context) by the same ideology. For that reason alone, the shooting-itself-in-the-foot stance of the ASTI, whether thought-through, simply visceral or just blundering, merits more than scorn.

Theirs represents a grassroots reaction to a model of macro economic management which is seen as a pillar of the boom economy. Fair enough. But the PPF is also a pillar of the boom economy's problems and inequalities.

If, on the practical paper, the union deserves a "fail" grade (which it probably does), on the theoretical one, it is in the "honour" category. To argue otherwise is not just to accept consensus but to ignore the risk of a form of commercial totalitarianism.

We can be certain that not all teachers are concerned about the "soul" of teaching. But the best ones are. It's a nebulous matter, of course, and utterly at odds with the realpolitik of industrial relations. None the less, when principle and practice are rendered irreconcilable, there is clearly some kind of unhealthy disjunction. Why should the ASTI have to be part of the PPF? The reasonable answer is because if it can cut special deals, then others will want out of the programme too.

That's only common sense. But it invariably makes good sense to question how and why notions of "common sense" are promoted. After all, not so long ago, it was the ultimate in common sense to seek a secure job for life, and teaching was among such jobs. Now it's common sense to regard such an ambition (or lack of ambition) as a waste of a life. Times change. Different forces come to the fore. So it goes. But it must always be education's job to question prevailing orthodoxies, even if Irish schools' track record in this regard is pitiful.

It's certainly true that when the prevailing forces - Catholic Church, the job-for-life mentality, the determinants of status - favoured teaching, that teachers were, by and large, a conservative bunch. That's human. Why would they advocate change when they were doing quite well?

The same principle applies to supporters of the PPF today. The current dispute may radicalise teachers however, because standing on a picket line is, if nothing else, what education management-speak calls "a learning experience".

There has always been an authoritarian strain in Irish teaching. If this dispute focuses teachers' minds (and, in turn, their pupils' minds) on the authoritarian demands of the market, the hard lesson of it all can salvage something important: what education actually means.