ON the first day of school this fall, Missouri high school students received a brochure entitled ''Juveniles and the Law'' along with their class schedules.
Prepared by the Missouri Bar Association, the pamphlet informs students about the state's tough new laws against young delinquents. ''Your juvenile record can follow you forever,'' it warns.
Like many states with rising juvenile crime, Missouri is getting tough on teen offenders. A new state law removes the veil of secrecy that once kept juvenile court proceedings private - in the hope that allowing names and photos in newspapers will discourage teen crime and alert school officials.
As the public pushes for more serious consequences to juvenile offenses and schools demand to know the background of students showing up in their classrooms, states across the nation are passing stricter laws and opening access to juvenile court records.
''Public officials are responding to the public perception that there is a problem with the juvenile-justice system,'' says Kimberly
Kempf-Leonard, a professor of criminology at the University of Missouri in St. Louis.
In 1980, only six states provided public access to juvenile court records. Today, 26 states have such laws.
The get-tough attitude is showing up everywhere. Cities are imposing evening curfews, more teenagers are being tried as adults, and federal law now requires one-year expulsions for students carrying guns to school.
Last year's legislative session was a busy one; at least 11 states tightened their juvenile-justice laws.
* Texas revised its juvenile-court system so that offenders as young as 10 can now be sentenced to 40 years incarceration.
r Kansas opened juvenile records for all offenders 14 or older.
* Mississippi required public identification of juvenile offenders who are convicted of illegal gun possession or multiple felonies.
* Virginia began requiring juvenile courts to notify school officials if a student is charged with an act of violence.
''States are trying to deal with juvenile offenders earlier and trying to look at the problem from a front-end perspective,'' says Jay Kroshus of the National Conference of State Legislatures in Denver. ''There are 50 incubators out there trying to figure out how to deal with this problem.''
Some states are passing laws that make parents parties to their children's actions. This forces their participation in counseling or treatment programs. In Oregon, a parent can be charged with a misdemeanor for refusing to cooperate.
Minnesota and several other states recently enacted laws enabling judges to give double sentences to serious offenders. This means a juvenile sentence can last until the defendant turns 21, and a suspended adult sentence can be imposed if the juvenile does not stay out of trouble.
Supporters view this as a compromise between the push to punish youthful offenders and the urge to rehabilitate them whenever possible. Critics charge that these get-tough approaches are unfair because they brand teens as criminals at an early age, even for petty crimes. They also note that putting youths behind bars will only turn them into hardened adult criminals.
THE alarming increase in juvenile crime and changing demographics are driving this flurry of new legislation. Youth violence has been rising steadily since 1985, even as the number of teens declined, according to a new Federal Bureau of Investigation report. As the 14-to-17-year-old age group is expected to grow, this trend could worsen.
Juvenile courts were set up nearly a century ago as a way to provide help for young delinquents, and today, all 50 states have separate juvenile-justice systems. But critics charge that the separate youth system is a lax, ineffective luxury that American society can no longer afford.
''Often, there are no attorneys involved, and there has traditionally been a cloak of confidentiality aimed at protecting the kids,'' says Professor Kempf-Leonard.
During the last 15 years, states have been remodeling their juvenile-justice systems to resemble the adult criminal courts. Yet, they have not changed the basic structure of the system to provide the same advocacy for youth offenders that adult offenders receive from lawyers and prisoner-rights laws, Kempf-Leonard argues.
A rethinking of the entire system is required, says Barry Feld, a professor of law at the University of Minnesota in Minneapolis. He argues that the juvenile courts should be abolished and serious young delinquents should be tried in adult criminal courts.
''The idea of the juvenile court is a wrong one,'' says Mr. Feld. ''It's a justice system that is punishing offenders using procedures that no adult would consent to be tried under.''
One alternative is now being debated in Michigan's state legislature. Lawmakers propose to eliminate the separate juvenile-court system and create a juvenile division within the adult court.