Greek fishermen paint eyes on their boats to ward off evil; we do the same thing with funny-shaped vegetables
I realised the other day that I am currently in the grip of two powerful superstitions, despite a complete indifference to broken mirrors and a lifetime's aversion to the astrologically challenged (when believers ask me what my star sign is I lie on principle, for the private pleasure of seeing them nod sagely and say "Yes, I thought so"). And what makes my own knots of credulity so difficult to unpick is that they are both rational superstitions - largely ritual gestures built on a thin foundation of reasoned judgement.

The first of these superstitions involves Kumon maths, a Korean educational programme for children designed to improve their numeracy and concentration. I was introduced to this by the approval of other middle-class parents, who hymned the benefits of improved concentration and confidence it had conferred on their children. And it does make sense, of course; by obliging your child to do a little bit of homework every day you hope to make up for the deficiencies of the state education system as well as reinforcing your sense of yourself as a caring parent.

What's more, it appears to have worked with my oldest son, whose ability to count and write numbers has improved considerably since he began the course. But at what an agonising emotional cost these improvements have been purchased! What grief and howling follow from my insistence that the work is completed. In our darkest moments I have wondered whether the entire Kumon organisation is a sinister plot to suborn our children - a paranoia only amplified by the occasional reverent newsletter, with its devotional references to the Founder and photographs of model pupils completing their homework on roller coasters and holiday Lilos. One day, perhaps, there will be a secret signal from Seoul or Pyongyang and legions of British children will march on Wembley, where they will perform quadratic equations in perfect synchrony.

I have lost count of the number of times I have sworn to abandon this pedagogic cult - and sworn obscenely too. But we are still there, gripped by a faith in its magical efficacy (there is no control for the experiment, naturally, so I have no firm way of knowing whether my son is better off or not - or indeed, whether the gloom he feels outweighs the intellectual benefits). Cancellation would seem to be a needless provocation to the gods of failure.

The second of these rational superstitions is my household's involvement in an organic home delivery arrangement. Every week a pleasant young man rings to ask what vegetables and fruit we would like to order and every Friday night I pop round to pick up the goods from a neighbour's porch, a paper-bagged cornucopia of unmolested fruit and vegetables (unmolested by humans anyway). This sounds wonderful on paper, I know - a small blow struck against the corporate food barons and in favour of family health.

But again the practice is not quite as wonderful as the theory. There's the problem of dirt to begin with. I know that I should rejoice in the honest clods of humus which cling to the roots, that every accompanying bug is an endorsement of the benign, toxin-free nature of the food, but new habits are hard to break. And while it's mildly comforting to know that everything has come from a farm where the soil isn't drenched in organophosphates, you do wonder why so much of the farm has to come along as well. If every customer washes as much topsoil down the drains as I do, I'm a bit concerned for its future. The potatoes are friable boulders of loam, and the carrots emerge like long-buried amphorae. Using these vegetables isn't cooking - it's a kind of archaeology.

Most blasphemous of all (I hardly dare write this) - they don't taste any better than the supermarket variety. Sometimes they actually taste worse; since we commenced our devotions, we have eaten watery carrots, mealy apples, flaccid greens. I confess that this is partly due to a mismatch of lifestyle and commodity. Whether it is because the organic distribution network is less efficient than the big chains' blitzkrieg methods, or because the food contains no preservatives, it simply doesn't last very long. It's positively eerie how quickly it goes off; you turn away to pick up a utensil and when you look back the stuff has started to decay, like one of those time-lapse films of an apple deflating under a surf of mould. So just one take-away pizza can result in throwing food away - a waste which entirely contradicts the green principles which underwrite the business in the first place.

When you voice such doubts, the true believers reply with horror stories about supermarket fruit. Did you know, they say, eyes rounded in disgust, that apples are polished with pork fat! Well, I didn't, and I can see this might give you pause if you were a devout Jew or Muslim. But I'm not and I quite like the shine. (In any case, if the Amish, say, had been polishing their apples with pork fat for the last 100 years then you would almost certainly find small ads in The New Yorker, offering gift-wrapped baskets of Hog Burnished Dessert Apples as a thoughtful gourmet gift.) I am tired of cutting out rotten bits, fed up with opening the vegetable drawer to find a jungle of potato sprouts reaching like triffids for the light. But even so, when the man rings, I mumble out another order. In both cases I long to abandon my dutiful observance but hesitate on the brink, fearful that in doing so I will consign my children to a career in fast food or myself to a lingering death from colon cancer. Greek fisherman paint an eye on the prow of their boats to ward off evil; in Crouch End, we do the same thing with counting practice and funny-shaped vegetablesn