Washington ? The Supreme Court ruled unanimously Tuesday that students may grade each other’s work in class without violating federal privacy law, deciding the case of a learning disabled boy whose classmates ridiculed his scores and called him a “dummy.”

The 9-0 ruling upheld the common schoolroom practice of having students swap homework, quizzes or other schoolwork and then correct one another’s work as the teacher goes over it aloud. Sometimes the teacher then has students call out the results, and the teacher records them.

“Correcting a classmate’s work can be as much a part of the assignment as taking the test itself,” Justice Anthony M. Kennedy wrote for himself and seven colleagues. Justice Antonin Scalia filed a separate concurring opinion.

“It is a way to teach material again in a new context, and it helps show students how to assist and respect fellow pupils,” Kennedy wrote.

An Oklahoma mother challenged the practice as embarrassing and a violation of a federal law protecting the privacy of student education records, such as a transcript.

Kristja Falvo’s case became a battle between the education establishment and conservative groups interested in promoting parental rights in schools.

Students and teachers should not have the power to reveal another student’s record without a parent’s permission, Falvo and her supporters argued.

Her children’s school, joined by other school districts and the Bush administration, argued that the 1974 privacy law was not meant to be read that way.

During November’s oral argument session in Falvo’s case, a few justices waxed nostalgic about their own school days, or about such seemingly harmless customs as the awarding of a gold star for good work.

On Tuesday, Kennedy noted that Falvo’s lawyer had seemed to argue “that if a teacher in any of the thousands of covered classrooms in the nation puts a happy face, a gold star or a disapproving remark on a classroom assignment, federal law does not allow other students to see it.”

“We doubt Congress meant to intervene in this drastic fashion,” Kennedy wrote.

Falvo said Tuesday that she has been contacted by parents throughout the country who object to the grading practice, and she still hopes to see it end. Congress could ban the practice, or schools could discontinue it on their own, she said.

“Maybe they won’t use it, because sometimes something legal isn’t healthy,” she said.

In other action Tuesday, the court:

Agreed to decide how far states may go in posting registries of sex offenders on the Internet after the offenders have finished their sentences and are released.

Upheld a 1988 law allowing for the eviction of families from public housing projects for the drug use of one member.

Refused to consider a plea to make it harder for cable companies to be sued by others involved in the pay-per-view market.

Dillard’s judgment upheld.