A nonprofit advocacy group says that students are being turned away from public schools in Pennsylvania because school districts aren't adhering to state laws regarding enrollment.

The Education Law Center said the errors involving enrollment inconvenience parents and adversely affect children, particularly foster children and immigrants, who cannot afford a delay in access to education.

A nine-page letter, dated Friday, was sent to the state Department of Education requesting a state investigation of school district enrollment practices based on violations it compiled by reviewing enrollment information posted on school district Web sites.

Because only 278 districts have enrollment information posted online, it said, the problems may be more widespread than the center was able to determine. The letter was posted on the center's Web site at www.elc-pa.org.

Department spokesman Michael Race yesterday confirmed receipt of the letter but declined comment.

The center said in the letter that it has intervened in 270 cases during the past school year in which families had difficulty enrolling students. It said some districts improperly demand a child's Social Security card, a parent's photo identification or court custody order, or inquire into immigration status as a condition of enrollment.

It said a handful of districts also violated the state law requiring that children be enrolled no later than five days after parents, guardians or caretakers submit registration materials.

The list of districts alleged to be in violation of state law or state guidelines was not posted, and Maura McInerney, an Education Law Center staff attorney in Philadelphia, said the names wouldn't be made public. Mr. Race didn't immediately respond to a request to release the names.

Ms. McInerney said problems were found in southwestern Pennsylvania and "really across the state." She said the center doesn't want to punish districts, just see their policies corrected.

Ira Weiss, solicitor for the Pittsburgh Public Schools and other local districts, said the center had not contacted him with complaints about his clients' enrollment policies.

Emily J. Leader, deputy chief counsel for the Pennsylvania School Boards Association, said she didn't believe that every practice the center assailed in its letter was inappropriate. In other cases, Ms. Leader said, districts might be following outdated regulations or making good-faith efforts to identify students trying to enroll under false pretenses.

"It happens all over the state, all the time," she said of efforts to skirt enrollment guidelines.

In general, the center says 162 districts were too explicit in the documents they demanded to establish residency, guardianship or caretaker status or demanded more health records than families are obligated to provide.

For example, the center said 28 districts require a parent's photo ID, something it says isn't allowed. It said some require a birth certificate when districts also should accept baptismal certificates or other documents.

Some families, it said, don't have photo IDs or birth certificates.

"I have to tell you, there are kids sitting out for weeks at a time -- on occasion, months at a time -- because school districts require documentation they don't have," Ms. McInerney said.