WASHINGTON (AP) _ The Supreme Court today refused to revive a Mississippi law that would have allowed student-led group prayers in public schools _ at assemblies and sports events and even in classrooms.

The justices, without comment, left intact rulings that declared the 1994 state law a violation of the constitutionally required separation of church and state.

Today's court action was not a ruling on the merits of the Mississippi law and set no national precedent. Confusion still reigns over just what the Constitution allows.

In other action, the court:

_Rejected an appeal by millionaire equestrian George Lindemann Jr., who is serving a 33-month federal prison term for insurance fraud stemming from the 1990 electrocution of one of his horses.

_Made it easier for federal courts to uphold criminal convictions by ruling that some state court trial errors were harmless. In an unsigned opinion, the justices reinstated a California man's murder conviction and told a federal appeals court to reconsider whether the use of a flawed jury instruction during his trial should be considered a harmless error.

In the debate over school prayer, the National School Boards Association last year told the justices in another dispute that the nation's public schools ``are currently the site of religious warfare'' and that ``school boards are caught in the middle and do not know which way to turn.''

The invalidated Mississippi law would have allowed ``invocations, benedictions or nonsectarian, non-proselytizing student-initiated voluntary prayer'' at ``school-related student events.''

Since a 1962 Supreme Court ruling, organized school prayers have been barred from public schools. But that landmark case involved prayer sessions sponsored and led by public school officials, not students.

The court, of course, never has banned individual prayer from public schools. Students remain free to pray before lunch, before tests or even during class if they do so in an unobtrusive way.

The justices in 1992 strengthened the ban on officially sponsored worship in public schools by prohibiting clergy-led prayers at public school graduation ceremonies.

But the 5th U.S. Circuit Court of Appeals _ in a decision that still is binding law in Mississippi, Louisiana and Texas _ subsequently ruled that the 1992 decision did not apply to graduation prayers planned and led by graduating seniors.

The Supreme Court silently left that ruling intact in 1993. But another federal appeals court has declared such student-led graduation prayers unlawful.

The Mississippi law, designed to go beyond graduation ceremonies, was enacted shortly after a widely publicized incident in which a Jackson high school principal was disciplined for allowing students to recite prayers over the school public address system while students were required to be in their classrooms.

The Mississippi Senate passed a resolution commending the principal for being a ``catalyst for a renewed effort all over this state and nation to return prayer to our public schools.''

Several days later, the state Senate and House of Representatives passed the school-prayer law.

David Ingebretsen, executive director of the state American Civil Liberties Union, and his daughter were among 14 individuals who sued to block the law from taking effect.

U.S. District Judge Henry Wingate ruled that the law was unconstitutional, except when applied to graduation ceremonies.

A three-judge panel of the 5th Circuit court upheld his ruling, and the entire appeals court voted 9-6 not to reconsider that ruling.

Leading the dissenters, Judge Edith Jones said the trial judge went too far in ``striking down Mississippi's attempt to accommodate students' desire _ and constitutional right _ voluntarily to pray aloud at school'' before it ever had been invoked by any student.

Jones previously had authored the 5th Circuit court's ruling that allowed student-led graduation prayers.

In the appeal acted on today, Mississippi Attorney General Mike Moore argued that the law should not have been invalidated before it ever took effect. ``The statute on its face does not mandate than any religious speech or prayer occur at all at any time,'' he said. ``Instead this is left to private choice.''

Opponents of the law urged the justices to reject the state's appeal, saying that the lower court rulings did nothing ``to deprive any students of any independently existing constitutional right to pray in public schools.''

The case is Moore vs. Ingebretsen, 96-331.