Attorney General Eric Holder said Thursday that all schools must enroll illegal immigrants as students, citing “troubling reports” that some districts are discriminating against the children of undocumented parents.

“Public school districts have an obligation to enroll students regardless of immigration status and without discrimination on the basis of race, color, or national origin,” Mr. Holder said in a statement released Thursday by the Justice Department. He said the department will do “everything it can” to make sure schools meet this obligation.

Mr. Holder was joined by Education Secretary Arne Duncan in issuing the new guidance to school administrators, telling them to be more flexible in accepting some documents from illegal parents and not to require others that may prove a child’s age and residence. The guidance is an update to earlier guidelines the Justice Department issued to school systems in 2011.

Although schools have a right to establish a child’s residency in a district, they don’t need to require the parents to have state-issued driver’s licenses or Social Security cards to prove they are in the country legally, the new guidelines state. Parents can produce a utility bill or a lease as a substitute.

The guidance is based on a 1982 Supreme Court decision that says children of illegal immigrants have a right to a public education. In Plyler v. Doe, the court struck down a Texas statute that denied funding for education to the children of illegal immigrants and a school district’s attempt to charge undocumented persons an annual $1,000 tuition fee for each illegal immigrant student.