By KIRK SEMPLE

Federal officials issued a memorandum to the nation’s school districts on Friday saying it was against the law for education officials to seek information that might reveal the immigration status of children applying for enrollment.

Civil liberties advocates and others have complained in recent months that many school districts are seeking children’s immigration papers as a prerequisite for enrollment. Some state and local officials have also considered bills to require prospective students to reveal their citizenship or immigration status.

“We have become aware of student enrollment practices that may chill or discourage the participation, or lead to the exclusion, of students based on their or their parents’ or guardians’ actual or perceived citizenship or immigration status,” said the memo, from Justice and Education Department officials. “These practices contravene federal law.”

The letter cited a 1982 Supreme Court decision that recognized the right of all children, regardless of immigration status, to attend public school as long as they met the age and residency requirements set by state law.

“The undocumented or noncitizen status of a student (or his or her parent or guardian) is irrelevant to that student’s entitlement to an elementary and secondary public school education,” said the memo, signed by Thomas E. Perez, assistant attorney general for the civil rights division of the Justice Department; Russlynn H. Ali, assistant secretary for civil rights in the Education Department; and Charles P. Rose, that department’s general counsel.

Xochitl Hinojosa, a Justice Department spokeswoman, said it was the first time her agency had issued guidance to school districts on the 1982 decision. The Education Department did not return calls seeking comment.

Civil liberties advocates, who had been asking President Obama’s administration to clarify the law, hailed the memo. “We’re gratified that the Department of Justice has seen fit to do the right thing, to clarify any ambiguities,” said Donna Lieberman, executive director of the New York Civil Liberties Union, calling the guidance “a really big deal.”

Last year, Ms. Lieberman’s group found that 139 districts in New York State — about 20 percent of the total — were requiring children’s immigration papers as a prerequisite to enrollment, or asking parents for information that only lawful immigrants could provide.

While the group did not find any cases in which children had been turned away for lack of immigration paperwork, it warned that the requirements could deter illegal immigrant families from enrolling children for fear that their status might be reported to federal authorities.

After months of pressure from the civil liberties group, the state’s Education Departmentsent school districts a memo strongly recommending that they not ask for information that might reveal the immigration status of enrolling students. State education officials in Maryland, New Jersey, Illinois and Nebraska have taken steps in recent years to halt similar practices, immigrant advocates said.

Despite the New York memo, some school districts there continued to press for the right to ask about immigration status, said Udi Ofer, advocacy director of the New York Civil Liberties Union. In Arizona, state lawmakers have considered a bill that would require the state’s Education Department to determine the number of public school students who are unable to prove lawful presence in the United States, officials said. Last year, a legislative committee in Oklahoma favored a bill to require public schools to determine, at the time of enrollment, whether a child was born outside the United States