Could you pass the teenager test?

Scene 1: It's the end-of-year school concert at your child's convent school. Aren't they sweet, you think, those beautiful girls in their unflattering uniforms, shiny hair, shiny faces, so confident, so poised, so . . . innocent?

Scene 2: Sunday evening at the local leisureplex. At this table, a gang of lads is hanging out, yapping away on mobile phones. In stroll two young wans, one confident, who makes straight for the lads, her prettier model-thin friend shyer but vulnerably lovely in her pedal pushers and skimpy top. About 14, you guess, glad you're not her mother. And yes, she's probably one of those convent girls.

Life can be tough for parents of teenagers. But it's tough for the kids too, under pressure from parents and school and themselves to be good students who'll score high points on their way to a brilliant career, as well as being cool, fashionably dressed, and in with the In crowd.

Parents have been worrying about teenagers ever since they were invented, somewhere around the 1940s. Before then, puberty seemed to be a short-lived affair for most people, at best a year or so between childhood and being packed off to work with instructions to hand over your wage packet at the end of the week. Betteroff adolescents were packed off to boarding school and locked away from trouble for the difficult years.

Like sex, teenagers appear to have arrived later here than in places like the US, so parents who grew up in the 1960s, even the 1970s, can remember a time when adolescents more or less did what they were told and didn't expect to get a life until they were at least sweet 16.

But in the 1990s, teenagerhood has never started so early, or ended so late, and even young-ish parents are having difficulty coming to terms with the very different world in which their children are growing up. Indeed, since the first signs of puberty and raging hormones can be detected in children as young as nine and 10, and children's financial dependency can last up to about 25, we might want to find a new, more accurate word than "teenage".

In any group of parents, you will find very different attitudes toward what is acceptable behaviour for teenage children. Should 12-year-olds go to discos, 13-year-olds go into town by themselves, 16-year-olds drink, 17-year-olds be trusted in the house by themselves for a week while you go on holidays? Not to mention sex. Should you discuss contraception, provide condoms, state your position on teenage sex and hope for the best?

Before your kids turn 11 or 12, some of these answers may seem obvious. A few years on, you sit outside a pub one evening, waiting to see if your 17-year-old and her friends will get in with their fake ID, and think guiltily about how you were once so sure that your children wouldn't drink underage (As one mother says, if you drive them to the pub, at least you know where they are).

The first rule of parenthood, but especially of teen parenthood is: don't be smug. A group of parents whose eldest child is on the brink of teenagerhood will often have pretty strong views on the boundaries they'll set when their child is a fully-fledged adolescent: no discos until they're 15, one will say. Certainly no alcohol. Well, duh, no sex. They'll be full of good intentions about listening to their children, keeping the lines of communication open.

But it's really hard to predict the reality: talk to the group five or six years on and you'll find that at least one or two families have had to cope with kids who went seriously off the rails - got pregnant, did drugs, hung out with a bad crowd, dropped out of school early, got into trouble with the police, got anorexia, tried to harm themselves. This is the nightmare most parents fear, and it does happen, even in the most loving and caring families.

At the other end of the scale are the lucky parents, whose children have never done anything more outrageous than come home an hour late, and who are late developers, tackling all those firsts when they're older and hopefully better able to cope (The way things are nowadays, a child who doesn't drink alcohol until he/she is 17 is a late developer).

So can you get much help from a manual? If you're the kind of parent who reared your small children with Dr Spock or Penelope Leach in one hand, then you've probably already been searching the bookshelves for a knit-a-better-teenager manual.

Teenagers - The Agony, The Ecstasy, The Answers is the latest rather clumsily-titled book published in a pretty crowded field. It offers no revelations, but blends statistics about modern teenage behaviour and attitudes, and interviews with parents and teens, proffering advice for both at the end of each chapter.

The authors, Aidan Macfarlane and Ann McPherson, whose previous books include The New Diary of a Teenage Health Freak, have a fairly pragmatic attitude to teenage behaviour. They matter-of-factly outline how puberty starts nowadays in girls at around 11-and-a-half, and in boys around the age of 12, and how children are exposed to sex, illegal drugs and alcohol at increasingly young ages. Instead of railing against this, they give suggestions on how to steer teens through the years from 12 to 20 in the world as it is, rather than how some of us might like it to be.

And they point out the obvious to most of us who have teenagers: "Don't assume that looking after teenagers is necessarily going to be hell - for many people it turns out to be a very rewarding time."

The basics are, say the authors, to set limits, make your love and concern obvious, expect a "fair" degree of but not "absolute" honesty about what your teenagers are up to, to negotiate rather than issue commands, and keep your nerve, as for most families, things do turn out OK in the long run.

It has slightly controversial advice on difficult areas such as sex education, suggesting that you talk not just about sex but about contraception, too, when children are between seven and 10 - young enough to be curious, but not too old to be embarrassed (It's quite normal for teenage children not to want to talk to their parents about sex).

And although the book's attitudes on matters sexual may be a bit neutral for some Irish tastes, in general, the authors share the Relationships and Sexuality Education view that teenagers who are well informed are less likely to experiment with early sex.

Their other mantra is that "education and ambition is the best contraception" - although they also advise parents to leave condoms lying around, to ensure that teenagers have protection if they do go ahead and have sex. In the UK, the mean age of first sexual intercourse is between 16 and 17, and first sexual experimentation between 12 and 13. This seems young, but given the way Irish teens drink, and the incidence of teen pregnancies, it seems likely that their sexual behaviour is pretty much the same, although many parents will not want to believe this.

All teenage life is here, from 14-year-olds who get drunk, unbeknownst to their parents, to siblings who fight constantly and never help around the house (sadly, quite normal behaviour). The book is also helpful about bullying, divorce and separation, sex abuse, eating disorders and suicide - topics about which we all, sadly, almost know too much already.

The book rightly points out that for many of us, teenagers are good fun, nice people to be with a lot of the time, and definitely good at puncturing parental pomposity. Any parent who gets upset at being told to "chill out", as the book suggests, deserves to be punctured.

A lot of parents who grew up in the 1960s and 1970s felt - before their babies turned 12 - that they would understand teenagers better than their own parents did. It's still a shock when we realise that our own anti-authoritarian attitudes have come home to roost in our quite young children. We can love their confidence, while still being shocked at what seems like their arrogance. More than one parent interviewed in this book talks about having responsibility for their children (because many are dependent well into their 20s) but no control, and a lot of us know what that feels like.

And, of course, what many of us didn't anticipate is the unchangeable fact of parenthood - that you never really do stop feeling responsible. It is really hard to let go, to let your child finish the job of growing up. The first time you let your firstborn go to a late-night disco, go away to college, go to America on the J1 visa, is just as nerve-wracking as the first time you let them cross a road by themselves. And it's probably worth spelling out to young teenagers that your bottom line is concern for their safety - the teenagers in this book do seem to appreciate this kind of concern, even when they think parents are over-protective.

Parents shouldn't be too hard on themselves: "When all is said and done, if, at the end of the day, your teenagers have done some drugs, experimented with sex, smoked some tobacco and been drunk a number of times - and you and they are still talking and like one another - consider that you as parents, and they as teenagers, have done well," say Macfarlane and McPherson.

Not high standards, perhaps, but a realistic test a lot of us could pass.

Teenagers - the Agony, the Ecstasy, the Answers by Aidan Macfarlane and Ann McPherson is published by Little, Brown and Company, price £9.99 in UK