Claire Harvey: If you can't ask mum, tune into Supernanny

Now remember," said the midwife, smiling that benign smile they must teach at midwifery courses, "walk or talk, don't shake."

The midwife, Sally, had come to visit a dear girlfriend of mine and her week-old baby, and we were all sitting in the living room having a cup of tea and listening to Sally say "mmm" (another midwifery-school trait) as my friend detailed the baby's progress.

Sally didn't look at either of us while she delivered her unexpected advice, just kept smiling directly at the still-squashed newborn face, dozing in the crook of her right arm.

It took a few moments for the meaning of this gentle warning to become apparent. What Sally's catchy little phrase meant was "no matter how vile and monstrous this baby becomes, don't you dare shake her". But there was no apparent evidence to suggest either of us was a closet baby-shaker, and the powdery snoozing rosebud didn't look capable of doing anything to provoke even mild irritation, let alone violence.

Neither of us could think of anything to say in response, so we all kept sipping tea in slightly embarrassed silence, apart from Sally's occasional "mmming" to the baby.

Sally wasn't accusing my friend of being a child abuser; she was just doing her job and making sure we knew that shaking babies was not a good idea.

Perhaps she felt a little self-conscious about having to say it at all, hence the averted eyes and gentle sing-song tone she used.

It was a little difficult not to take offence - of course we knew not to shake a baby, how could she even think such a thing? - but that quiet remark was an interesting insight into the world of parenthood.

Paediatric professionals must deal every day with new mothers and fathers who know practically nothing about children.

Fifty years ago, young women like my friend and I could be safely assumed to be reasonably competent child-wranglers. If we didn't already have children of our own, we would have at least watched and helped our own mothers and sisters dealing with babies.

We would have changed nappies and administered rusks and extracted scissors from small sticky fists, and observed that you can't stop the crying with a vigorous shake, no matter how tempting it might seem.

Today, many new parents must effectively teach themselves how to raise children, and cope with fevers and rashes and choking episodes without a grandparent or auntie or sister to call on for advice.

Humans have spent centuries acquiring all the little tricks of parenthood and passing that knowledge down the generations, but now many parents must learn it from scratch, alone or with just an equally uninformed partner for support; a prospect as terrifying for them as it must be for midwives.

That is where reality television comes in - the genre the TV snobs loathe most, the type of programming which is supposed to represent everything that is lowbrow and dumb about modern mass entertainment.

At first, shows such as Supernanny and Little Angels look like little more than more pseudo-documentary prurience, the opportunity for viewers to sneer with smug satisfaction at the sight of others' misfortune and bad behaviour.

There is definitely an element of that sort of schadenfreude on these shows; harried parents trying to deal with the hideous screechings of ankle-biters so savage and foul-mouthed they would be more suited to the parliamentary cross-benches than to kindergarten.

You might think exposing this kind of extreme carnage would turn prospective parents off having children, much as the horrors of Celebrity Treasure Island would turn off any sensible viewer from travelling to Fiji with washed-up rugby league players.

But the real message of Supernanny is that every child is potentially wonderful, with the right kind of parenting.

The real message is redemption; no matter how revolting the children are at the beginning of the show (like last week's mini-Satan, aged 5, who called his mother a bitch and split her lip with his right hook), Supernanny invariably proves that underneath they are just tiny souls in search of the right kind of love, the firm and safe and reliable kind. These kids want their parents to take charge; they're miserable at being allowed to go so wild that nobody can get close enough to hug them.

That's where this kind of telly is more than just entertainment, it's the education and support many of us don't get from our familial or social networks .

Reality programming might not have been what the drafters of TVNZ's lofty charter were thinking of when they exhorted "programming of an educational nature that support[s] learning and the personal development of New Zealanders", but the supernannies are a good deal more useful than some more superficially worthy shows which purport to inform or educate.