Their behavior always has been annoying and sometimes even troublesome. Suddenly, though, America's teenagers have turned into Public Enemy Number One, targets of a growing number of increasingly harsh measures by parents and public institutions aimed at yanking them into line.

Pick up any high school newspaper to sample the outrage of teenagers suffering death by a thousand cuts: Breathalyzer tests to get into the prom or a urinalysis to get a driver's license; nighttime lockouts at shopping malls and toddlerlike lock-ins in "time out" classrooms; dogs sniffing lockers for drugs, metal detectors searching backpacks for weapons and dress codes prohibiting gang-suggestive black lipstick and bandanas.Now add to that Gov. William F. Weld's bill, proposed last week, to require Massachusetts teenagers to present letters certifying regular school attendance when they apply for driver's permits and licenses. Under it, truants later could have their licenses revoked.

It was never like this in the '60s. Then, as Janis Joplin warbled in a drug-altered state, freedom was just another word for nothing left to lose. Yet now, in the name of protecting both their children and the public safety, the baby boomers who broke so much china in their youth are applying their hallmark drive and will to denying liberties to their children.

"Their baby boomer parents, who grew up experimenting and pushing boundaries, are not just strict, they are draconian," said Mike Males, author of "The Scapegoat Generation: America's War on Adolescents." "It's zero tolerance time."

In defense of zero tolerance, parents and public officials quickly point out that it's a dangerous, even depraved world out there. If it was never like this in the '60s, it's because the '60s were not the '90s. Violent juvenile crime, until quite recently, had been skyrocketing. Drug use, particularly marijuana, is way up among teenagers. Sexual intercourse carries the HIV risk that it didn't 30 years ago. Truancy these days leads to trouble with police and arrest records. A parents group in Anchorage recently tried to buy up all the tickets to a concert of the shock-rock group Marilyn Manson, something that probably would not have happened if the Monkees had come to town.

President Clinton, a baby boomer and the father of a teenager, perfectly read and reflected the fear and anxiety on the face of the nation during last year's campaign, and devised a second-term, parent-friendly agenda aimed at what he calls teenage "order and discipline." He called for school uniforms and town curfews; drug testing for teenagers seeking driver's licenses; "zero tolerance" for guns in schools and teenage drunken driving; and millions of dollars for antidrug and anti-smoking public-information campaigns aimed at children.

When he came to Boston last month, the president declared himself tough on youth crime, proposing a $500 million plan to give communities money to attack truancy, and to encourage what is unquestionably the most punitive and fastest-growing trend in juvenile justice: having violent offenders as young as 14 tried and sentenced as adults.

Within days, Weld - also an aging boomer and the father of teenagers - offered his legislative fix for truancy in the Commonwealth.

There's no body of evidence yet to prove that any of these newly minted rules and sanctions work; psychologists who specialize in adolescents say that while teenage behavior is malleable, it is molded much more by peers and the media than by the fear of punishment. James Alan Fox, dean of the College of Criminal Justice at Northeastern University, notes that nighttime curfews do little to curb teenage crime, which peaks from 3 to 8 p.m.

Still, the politicians, public officials, and parents are snapping back, abandoning permissive attitudes, and seeking to impose order on a generation that looks at risk and, at worst, out of control.

"Oh, the teenagers just hate it; they want their freedom back," said David Popenoe, a sociology professor at Rutgers University who writes extensively on family issues. "But the schools and families are realizing that a lot of kids are undersocialized because we've drifted too far from authority and parenting. The impulse now is to impose structure, set forth proper standards, and enforce codes of behavior."

Nancy Murray, who directs the Bill of Rights education project for the American Civil Liberties Union of Massachusetts, sees it as part of a far-reaching movement in the country to turn back the clock. "It's a culture war between those who say things went terribly wrong in the '60s, let's get shipshape and end the dissent, and those who still value freedom of expression."

For parents who grew up in the 1960s, it's painful to take sides in that culture war. It's even harder for members of the Woodstock generation to become in midlife what William Strauss, co-author of "The Fourth Turning," calls "moral megaphoners."

"Baby-boom parents aren't trying to punish their teenagers, they're trying to reform them, have the nation feel good about them," Strauss said. "The same protective impulses that had them declaring `Baby on Board' in their cars now have them demanding their kids shape up, get in line, cut it out, follow the rules, just say no - and we mean it!"

If teenagers are confused by the crackdown, it's understandable. They can't imagine their parents would have stood for V-chips censoring what television shows they watched, or "smut blockers" if the Internet had been around 30 years ago. In the 1960s, some high schools had smoking rooms; today, some high school yards are policed, and students are ticketed for smoking.

Parental responsibility for teenage behavior is taking other new forms in the 1990s. In January, the Food and Drug Administration approved an over-the-counter home urine-testing kit, which is being marketed directly to parents who want to learn if their children are using illegal drugs. And around the country, local ordinances that hold parents legally and financially responsible for their teenagers' misdeeds are catching on fast.

"Parents today are very conflicted; unlike their own parents, they had firsthand experience with sex, drugs and violence, and now they are scared with what's going on in society and want to shield their kids from sex, drugs and violence," said Dr. Victor Strasburger, chief of adolescent medicine at the Univesity of New Mexico School of Medicine and author of "Getting Your Kids to Say No in the '90s When You Said Yes in the '60s."

"It's an extraordinarily difficult time to be a teenager or a parent," Strasburger said. "Teenagers are stressed by peers, the media, commercialism, the need to exceed the expectations of their parents, and parents are equally stressed by money, blended families, divorce, and time pressures."

If stress creates generational problems in the middle class, it is multiplied many times over for teenagers living in poverty and often in fractured families scarred by abuse and threatened by everyday violence. Yet these youngsters, when they get in trouble or cause it, aren't viewed by adults as victims, but, increasingly, as demons to be feared.

In their recent book, "Body Count," William Bennett, drug czar under President Bush, and John DiIulio Jr., a professor of politics and public affairs at Princeton University, forecast a tidal wave of youth violence, cresting in the year 2005 and perpetrated by teenage "super-predators" - wild, cold-blooded, and remorseless killers raised in moral poverty. The label has been quoted widely, but not everywhere endorsed.

"Something more vicious, more punitive, more dehumanizing is going on right now in the nation's official response to teenagers," said Robert Schwartz, executive director of the Juvenile Law Center, a public-interest law firm in Philadelphia. "For the first time, we are willing to brand the behavior of acting-out juveniles as deviant and call for punishment that is an eye-for-an-eye."

The political response to a 62 percent increase in the rate of arrests for violent juvenile crime between 1987 and 1993 has been for some 47 states, including Massachusetts, to enact measures that automatically send certain youthful offenders into the adult judicial system. Despite a lack of data showing it has a deterrent effect or lowers recidivism rates among juveniles, the political power of the idea is so great that Congress is expected to pass a bill this year making it easier to try juveniles as adults in federal courts.

Meanwhile, the violent crime rate among juveniles dipped nearly 3 percent in 1995; birth rates among teenagers are falling, too, as is the use of crack cocaine; and even auto fatalities by young drivers are down. The Department of Health and Human Services, in a recent compilation of national surveys, found the majority of teenagers say they want to be successful and have families; a third regularly attend religious services; half exercise often; and most always wear seat belts.

"Teenagers aren't bad kids, they're good kids, idealistic and altruistic for the most part, and 80 percent of them get through these years with little, if any, difficulty," Strasburger said. "All it takes is a little feeding and watering, which is something adults don't always understand."