PARENTS want the best for their children. They love them and care about them, and research has shown that they believe their children will be more successful, wealthier, better educated, and more accomplished than they are themselves. So, for years, many parents cheerfully go about helping their children along the road to attaining these worthy goals. Why, then, do these beloved offspring reach their 12th or 13th birthdays and evolve into surly adolescents whose greatest joy lies in denouncing their parents and all that they stand for? How does an offensive (or promiscuous, or depressed, or besotted or otherwise rebellious) creature emerge from that formerly terrific little kid who thought his mom and dad were the greatest? And what on earth can his mom and dad do about it now?

Three new books on adolescents explore these problems and--with varying degrees of success--try to find a solution to the intergenerational angst that lately seems to be finding more and deadlier means of expression. According to Sam Janus, the psychologist who has written The Death of Innocence: How Our Children Are Endangered by the New Sexual Freedom, our kids are turning out badly thanks to the sexual revolution, which has cut their childhoods short, leaving them incapable of mature, loving relationships. It's an interesting idea, but the going almost immediately gets boggy, when it becomes clear that Janus considers incest, pedophilia, and child pornography and prostitution national outgrowths of the new sexual freedom. Despite his best efforts, it's pretty clear that the pathetic children involved in such behavior are victims not of "new freedom," but of old-fashioned abuse by seriously disturbed adults.

Janus writes movingly and persuasively of the sordid, dangerous life that faces virtually every runaway who drifts to the nation's cities, and it's shocking to read that the abused children he interviewed prefer an appalling life on the street to the prospect of returning to their homes. And such homes! According to The Death of Innocence, among prostitutes the incidence of sexual molestation in childhood is 92 percent, and 67 percent of them were sexually assaulted. At least three-quarters of runaways are escaping incestuous abuse, and about 70 percent of teen-aged drug addicts are victims of incest.

Horrifying statistics, but unfortunately, owing to Janus' unbelievably sloppy reference system, it's impossible to discover the source of this, or most of the factual material in his book. In fact, although Janus' work exposes a shameful situation and suggests that society must begin to respond to these sick households, The Death of Innocence is undermined throughout by its preachy tone, sloppy research, repetitiousness, and reliance on the hedge-your-bets school of reporting: make a statement, then back it up with barely related quotes from "name" experts. And, while it tackles an important problem, The Death of Innocence does little to help parents avoid similar disasters with their children. Stylistic oddities also give one pause: Janus refers to himself variously as "I," "we," "Sam Janus" and "the author," which gives one an unsettling feeling about the author himself. The result is unfortunately chaotic and confusing.

Psychologist David Elkind has taken a similar theme--that we pressure our children into growing up too fast--but has treated the topic coherently. With compassion for the parents, syeachools, and institutions that rush children into a premature parody of adulthood, Elkind carefully and persuasively outlines the forces that are creating very small children who look and talk like miniature adults, and very big adolescent children who behave with the self-restraint and wisdom of 2-year-olds.

The baffled, anxious teen-agers who become active sexually, take drugs, and seem unable to understand their own or others' needs, were created by a society, Elkind says, that is hurried. Hurried people, he argues, are stressed and egocentric; they are too overwhelmed by the pressures on their own lives to attend realistically to the needs of anyone else, even their own children. Instead, out of sync with their children's real needs and capacities, they rush their children academically, thrust sexual information upon them at inappropriate ages, and expect them to provide moral approval and justification for their parents' confused, stressed existences.

Of course, the children can't keep up with this pressure, at least not for long. The baby who's pushed into reading at 2, the 7-year-old pal who is her divorced mother's confidante, the child who is exposed to a blend of absurdly precocious TV children on "family fare" and violent outbursts on "adventure" shows, has been pushed too far. The stress caused by giving children power before they can handle responsibility is enormous, and results, Elkind says, in the real death of innocence: these overloaded children lose, far too young, the necessary sense that the world is safe and that their parents will protect them. Instead, they find often self-destructive ways to cope with this pressure: cult membership, academic failure, drugs, indiscriminant sexual activity, workaholism, an inability to form attachments, are just a few.

If Elkind had only explained the hurried-child phenomenon, his book would still have been impressive. Luckily, though, The Hurried Child is prescriptive as well, and includes useful tests to help parents gauge their relationships with their children. Elkind, however, is not without his quirks--his section on drug-pushing pop lyrics includes a lengthy pharmaceutical exegesis of "Hey Jude" and "Bridge Over Troubled Waters" that stretches credibility. But he's accepting of a variety of family styles, careful not to condemn lightly, and at core, both supportive of stressed parents and sanguine about their ability to slow themselves and their children down.

The Healthy Adolescent by Barry Lauton and Arthur S. Freese is, if anything, too supportive of parents. It's a reassuring, if shallow, compendium of facts and information about adolescent behavior, health, and development, and its underlying theme is "this too shall pass." The Healthy Adolescent is refreshing if only because it consistently presupposes the presence of one or two concerned parents in the adolescent's life.

Its bland but comforting tone may be welcomed by those dealing with minor crisis and confrontations. It's less help, however, for parents who are struggling to cope with a full-blown teen-age rebellion. The platitudinous knowledge that it helps to "demonstrate your love at all times and help placate your teen-ager's fears" wouldn't go far in aiding the angry parent who's exasperated by his child's reckless or illogical behavior. Similarly, to suggest in a chapter entitled "How to Improve Rapport" that "even if parents feel it is necessary to withhold approval, they should never withhold interest or love. Love must be expressed continuously even when there are sharp clashes" isn't likely to be very helpful in the middle of a such a clash.

The book is probably strongest on dealing with specific crises in an adolescent's life: chronic or acute illness, grief, and sexual activity are handled in a limited but sensitive manner. Throughout, though, the book is weak on psychology: statements such as' "teen-agers are strangely naive about VD" and promiscuity are likely to leave parentsts, syea who have bought this "manual" frustrated and poorly prepared to understand their children's thinking or behavior.

The Healthy Adolescent also has a strong, if unsurprising, pro-physician bias that often recommends that an ''adolescent specialist" take over some of the harder parental jobs, such as the provision of information about sex and contraception. However, to suggest as the authors do that a physician is "an ideal parent substitute" for a grieving teen- ager seems to be stretching a rather long bow.

Glaring omissions occur as well: the dilemma that faces a pregnant teen-ager is defined exclusively in terms of abortion or adoption--never is it mentioned that the pregnant young woman is more than likely to want to keep and raise her child. And, for a manual, the book is occasionally strangely unhelpful. In a section on nutrition, for example, it would have been useful if recommended nutritional requirements had been made more accessible: to learn that "good nutrition requires an intake of protein daily of one gram per kilogram of body weight from age 11 to age 14" is interesting but, barring a translation, is not of immediate use to most parents. Moreover, the authors don't even follow their own leads: although they mention that accidents are the No. 1 killer of one-to 15-year-olds, there's nothing in the book about how to deal with adolescents who take outrageous physical risks.

In fact, parents who really want to understand and help their children would do well to b this book, then leave it for their teen-ager to find and read (he'll begin to understand his parents' concerns for him). And then they would do well to go out and buy The Hurried Child for themselves.y