It's hard to understand why some publicans serve under-age drinkers. "Teenage drinkers are messier," says one bar owner. "They fight, throw up, get abusive - they lose control quickly."

All the reports and statistics that tell you teenage drinking is out of control probably wash over you - until your eldest child starts to drink. That could be at 12; more likely, he or she will want to start drinking at 15 or 16 - at least a third of 16-year-olds had taken a drink 20 or more times in the previous year, according to a recent Europe-wide study. By 17, the vast majority of teens - more than 70 per cent - are drinking on a fairly regular basis.

And we mean drinking. Spirits, and vodka in particular, seem to be the favoured teen-girl tipple; the lads, meanwhile, stick largely to pints.

The furore over "alcopops" was successful in reducing the market for them. Instead, the kids now love the alcopop-ish Bacardi Breezer, or Red Bull and vodka - a mix of the high-caffeine soft drink with a spirit that costs between £4.40 and £5 and is pretty much guaranteed to give you a quick high.

Drinking to get drunk is a growing part of teen culture. Should parents point out to teenagers how intoxicating spirits are, say, compared to beer or wine? The bar owner laughs: "They know already - that's why they drink them."

Jack Daniels, the American bourbon, is also currently quite chic with both boys and girls.

We can rail all we want about pubs serving teenagers - the law is broken routinely, with few prosecutions. Parents should assume that their children will, sooner or later, come under pressure to drink.

Teenagers need information not just about the risks, in general, of drinking; they also need to be educated about the effects of different kinds of drink and about how much is too much - to learn how to drink "sensibly".

Does teaching under-age teenagers how to drink compromise parents? After all, it implies tacit approval of their drinking. Should parents introduce them to it on family occasions, or on holiday?

The Department of Health's National Alcohol Policy seems to suggest as much. The thrust of this policy generally is to promote moderate drinking amongst all age groups; "the home is an environment where parents can, if they so wish, introduce their teenage son or daughter to alcohol in an open and natural setting," it says. (In fairness, we should note that the document is talking about children of legal drinking age.)

All these studies of teen drinking do throw up one useful fact: what parents say does influence their children's drinking behaviour. When 12- to 15-year-olds in a recent survey who did not drink were asked why not, they said, first, for health reasons and, second, because their parents forbade it.

This is a tricky area for parents, who waver between handing down old-fashioned diktats and feeling powerless to influence their children. "The baseline can be that parents tell their teenagers they don't want them to drink - but also let them know they can talk about it to them if they do start. If you shut down that avenue of information, they will turn to their peers," says Iris Elliott of the Eastern Health Board's Health Promotion Unit. Most parents of teenagers know that if you're too hardline, chances are they will simply lie to you. But if you're too "reasonable" you can find yourself doing things you never thought you would - like waiting outside a pub to see if your 16-year-old will get in with a fake ID.

The middle way seems to be to state your position clearly and to discuss drinking with them from early adolescence. First, and most important, is to review your own drinking habits: nothing you say about sensible drinking will mean anything if you abuse alcohol yourself. Marie Murray and Colm Keane, in their very useful book The Teenage Years, advise parents not to tell "amusing" stories about things people did when drunk, or say things like "I could murder a pint" or "He can really hold his drink" - all of which send out the wrong message about drinking.

Examine your conscience. Many of us might find we're confronting some home truths we've been trying to ignore; much of what passes for "social" drinking in adult life is actually way over the limit.

The long-term health risks of alcohol are less likely to worry teenagers than something more immediate - like making a fool of yourself, or getting pregnant after a one-night stand, or putting on weight. Mizz, one of those Brit teen magazines routinely accused of lowering teenagers' standards, put this message across effectively in a recent feature on alcohol. Kirsty (a frightening 14) says "I once had a bad experience drinking and ended up really embarrassing myself . . . it put me off drinking. I don't like the taste of alcohol anyway."

Mizz's message: "Don't drink. It's not big and it certainly isn't clever."

Many schools discuss substance abuse with both primary and post-primary children, so it's worth asking the school what it's teaching, so that you can re-inforce the message. Every health board has health promotion officers, from whom you can get free leaflets and information about alcohol.

Finally, don't think your troubles are over if they don't drink before they're 18 - because college drinking is, by all accounts, seriously out of control. But that's another story . . .