It was a big step for adolescentkind when the United States Supreme Court said 29 years ago that "students in school as well as out of school are persons under our Constitution."

Under the law, being a "person" entitles you to many rights and freedoms. And those came quickly in the remarkable decade beginning in the mid-1960's. Teen-agers won expanded rights to participate in political protest, the context of the Supreme Court's statement. They were granted greater constitutional protections, like the right to counsel, in juvenile court proceedings. They shook off dress codes and curfews. They were guaranteed the right to abortion without a parent's approval.

Even though the Supreme Court put to rest in the late 60's the centuries-old legal view that minors are simply their parents' property, it was soon circumscribing its own definitions of minors' constitutional rights.

But now "there is a turning-back-the-clock kind of slow movement," said Norman Siegel, the executive director of the New York Civil Liberties Union. "The shorthand is that teen-agers are beginning to lose whatever they did win.

"It's a control issue," Mr. Siegel continued. "What happened in a larger way is that the adult population got frightened and threatened by the teen-age population. They put a screeching halt to respect for individual rights of teen-agers."

Fear of teen-agers has also resulted in public demand for stricter treatment of minors accused of crimes. "The courts have been faced increasingly with youngsters who seem to have exhausted what the juvenile system has to offer," said Stanton Samenow, a psychologist. "Kids need to be held accountable for serious offenses."

In sum, in their everyday lives the law is treating teen-agers as if they are children, but in criminal matters it is treating them more like adults. It is a trend exemplified by an appeals court decision that upheld California's statutory rape law, which was challenged by a 16-year-old boy charged for having sex with a 14-year-old girl.

"There are freedoms which adults enjoy which are beyond those afforded minors," the court said this month. "Minors often lack the ability to make fully informed choices that take account of both immediate and long-range consequences."

Many schools are strengthening their supervision of student newspapers (or, from Mr. Siegel's perspective, censoring) and adopting conduct and dress codes. Some cities are imposing curfews, and every state but Louisiana has set its drinking age at 21.

Mostly, courts as well as voters have approved. Public Agenda, a public-policy research group, reported last year in a survey that "when asked what first comes to their minds when they think of today's teen-agers, two-thirds of Americans (67 percent of the 2,000 adults surveyed) immediately reach for negative adjectives such as rude, irresponsible and wild. Only a handful (12 percent) describe teens positively, using terms such as smart and helpful."

ADULTS might be reassured to know that the courts, which have become less expansive about everybody's civil liberties, have never made teen-agers the "persons" that adults are. Even though the Supreme Court put to rest in the late 60's the centuries-old legal view that minors are simply their parents' property, it was soon circumscribing its own definitions of minors' constitutional rights.

The Court has held, for example, that freedom-of-speech rights in schools do not prevent administrators from censoring speech they think will be disruptive. It has also upheld searches of students' purses and backpacks under circumstances that would not justify a police officer's search of an adult. And when teen-agers are in conflict with their parents, the courts are reluctant to interfere.

Parents do face increasing restrictions in many states in cases of abuse or neglect or when they try to deny medical treatment for their children, usually for religious reasons. New Federal legislation requires termination of parents' rights in certain circumstances, and while these cases rarely involve teen-agers, the law reflects a consensus that older children should have more voice in custody matters.

But teen-agers themselves often resist the termination of parents' rights, said Patrick T. Murphy, who heads the Public Guardians Office in Cook County, Ill., a government agency that represents abused and neglected children. Usually, Mr. Murphy said, his office respects those wishes, though it is meant to act in "the best interests of the child" rather than argue for the child's preference.

While many advocates for children say a teen-ager's wishes should prevail, Mr. Murphy said, "We don't give kids the right to vote or to buy liquor, and at some point you have to exercise adult judgment."

In the criminal realm, paternalism has given way to the view that teen-agers accused of serious crimes should be treated as adults. "The trend is to become more and more punitive," said Thomas F. Geraghty, a law professor and the director of the legal clinic at Northwestern University.

Professor Geraghty said this new stringency, apparent in recent laws adopted by virtually every state, is changing the very definition of juvenile justice. He pointed to the new juvenile court legislation in Illinois: while the old law's primary purpose was the "care and guidance" necessary for "the welfare of the minor," under the amended version the main goal is "a system that will protect the community" and "impose accountability for violations of law."

In the view of Dr. Samenow, the psychologist, the system is "responding to much more serious situations, much more hardened types of offenders."

Mr. Siegel, of the New York Civil Liberties Union, said the new rules are harder to challenge in court than the rules of 10 or 15 years ago. But the very imposition of this orthodoxy, he said, could revive an era of protests.

His office, he said, has recently seen an influx of teen-agers eager to repeal New York City's new school uniforms requirement. "It's reminiscent of that period in the late 1960's," Mr. Siegel said, "when students realized they had some power."

Laura Mansnerus is a reporter for The Times's Metropolitan news desk.