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, 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 Department sent 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.