Teachers are duty bound to take the general view (how on Earth are they going to march their 30-plus 11-year-olds through the history syllabus by the end of term?) while parents are biologically programmed to focus on the particular (what is my Susie getting out of this interminable project on the Victorians, and why does no one teach her how to spell "industrial"?).
It's the same with everything in the educational firmament, not least grant-maintained schools. In the overall scheme of things these schools are nasty, greedy institutions gobbling up an undue share of the educational budget, but if you are a parent with a shiny new opted-out school just down the road, to which little Susie (copiously primed on the Victorians) will progress after the summer holidays, you tend to give three cheers and not think twice about all the cash-starved comprehensives elsewhere.
This is exactly the situation in our local town, where the secondary school was, for years, a neglected comprehensive sliding into oblivion. Then it got a new head, a frank and fearless woman who gave off the kind of energy that made people feel anything was possible, even turning a rag-bag campus of temporary classrooms, scarred sports hall, and torpid schoolchildren into a beacon of excellence.
She sweated and pushed to get the school to go grant-maintained and within the year it was hitting local headlines for its improving exam results, its grand plans for new facilities, its musical ambitions, its specialist help for high-fliers and low achievers, and its intention to bring in a selective sixth form.
Now the word in the supermarket aisles is that this school is becoming quite something. Parents tell each other how good it is. Students are switching back from the far-flung schools they had been attending, and local private schools are beginning to take a keen and nervous interest in what is going on.
Of course, without such a wicked decline, the school could never have staged such a dramatic comeback. And, of course, too, it can only do what it is now doing because of the hefty injection of capital funds it received for going grant-maintained.
But to parents with students at the school, these are quibbles. What they see is simple transformation: a no-hope school gaining pride and purpose, and at last offering their children something worth having.
So there is relief locally that the Labour party has decided to allow opted-out schools to continue, albeit under a new name and with a certain tweaking of arrangements.
Because parents don't give a damn what schools are called, or exactly who sits on the governing body. But they care passionately about standards, discipline and school ethos, and if they've got something that produces results, they want to hang on to it, come what may, and no matter - frankly - who else misses out in the process.
The parent in Tony Blair understands this perfectly. There's no way, he has said, he would ever make decisions about his children's schooling on the grounds of political correctness. And so, not surprisingly, his party's document on GM schools, Diversity and Excellence, scarcely bothers with correctness of any kind.
It's a fancy piece of footwork. Under its paper-thin tissue of compromise, GM schools will become foundation schools, but with no special funding and an admissions policy based on local agreement, while local authority schools will get the same financial autonomy and more parents on their governing bodies.
Imagine explaining the difference to a visiting Martian. But if there is none, why bother with foundation schools at all? Especially if you are removing the massive dollops of start-up cash which have been their hallmark so far?
Because, says Labour, we need to encourage diversity. But what diversity is this? Storefront schools? Religious cult schools? Magnet schools with specialist curricula based on tourism or dance-drama? No, of course not. It's academic diversity. Or - whisper it not - selection.
What convoluted hoops we jump through when talking about education! How hard we work to try and pretend things are not what they are! Roy Hattersley is exactly right when he points out that what Labour is espousing is a divided education system without offering a single good reason for the divisions - except, of course, that trusty old favourite, not rocking the voters' boat.
Well, fine. Unlike Roy Hattersley, most parents prize continuity for their children far above ideological purity, and don't much mind if they have to embrace political fudge and mudge to get it. It's no more than they expect.
But there still remains a deep hollowness at the heart of it all. Is it really possible to square the circle? To permit ersatz grammar schools without recreating ersatz secondary moderns?
Of course not. So is this kind of diversity what we really want? And, if so, shouldn't we be willing to come out and say so openly, and to embrace the full consequences of such divisions, both good and bad?
And if we don't? Well, maybe we don't want Diversity and Excellence at all, but something far more simple, if, as we've already discovered, far harder to attain: Excellence and Excellence. And not just in our own particular, local schools, but in all schools everywhere.