The city’s ban on cell phones in schools is unconstitutional, a lawsuit filed yesterday by a group of parents claims.

The lead lawyer representing the eight parents in the case, Norman Siegel, said the Bloomberg administration has acted “illegally and unconstitutionally” and called the issue a matter of civil rights.

The suit, filed against the city’s Department of Education, Mayor Bloomberg, and the schools chancellor, Joel Klein, asks that children be allowed to carry their phones to and from school. It does not request they be able to use them during class.

“The ban on cell phones, very simply, needs to be lifted,” Mr. Siegel, who is the former head of the New York Civil Liberties Union, said.

He said that the ban is unconstitutional because it interferes with a parent’s right, guaranteed under the state and federal constitutions, to ensure the safety of their child.

Dozens of parents gathered across the street from the courts yesterday to plead their case to reporters.

“This is a safety issue,” a Bronx mother who is a plaintiff in the case, Camella Price, said. She was joined by her daughter, Lashea Suggs, who said she recently used her cell phone to call for help when a pack of teenagers followed her home and threatened to beat her up.

The city’s ban on cell phones dates to a 1988 policy that forbids students from carrying beepers and other electronic devices to school. In recent years, many schools opted not to enforce the ban as long as students turned off their phones during class and kept them out of sight. The issue flared up in April, when Mr. Bloomberg sent new portable metal detectors to schools in an effort to crack down on weapons in the classroom. The searches resulted in hundreds of cell phones being confiscated.

Mr. Bloomberg has refused to compromise on the issue, and has dismissed suggestions that schools find some way to accommodate student phones so that they can carry them to school for use outside the classroom.

While Mr. Bloomberg is now decentralizing the school system and allowing a quarter of school principals to opt out of the city’s regional system and make more decisions about how to run their schools, they will not be allowed to decide if they want to allow cell phones inside their buildings. The city’s teachers union also has come out against the ban and is calling on the city to let each school decide how to tackle the issue.

“We can’t yet comment on specifics of the lawsuit, but we stand by our policy,” a spokesman for the education department, Keith Kalb, said. “It is our experience that when cell phones are brought into schools, they are used and disrupt the school’s learning environment. There is no constitutional right to disrupt a student’s education.”