Cell phones have been at the center of numerous altercations at schools and students have used them to photograph an exam and trade sexually explicit photos, the top safety officer at the city’s Department of Education said in court papers filed in defense of the citywide ban on cell phones in public schools.

The ban is one of the most restrictive of its kind in place in a major American city. A lawsuit brought by several parents challenges the policy.

The ban is necessary because the use of cell phones “jeopardizes school safety and undermines the teaching and learning process,” the safety officer, Rose Albanese-DePinto, claimed in a recent affidavit. As evidence, Ms. Albenese-DePinto refers to more than 20 cell phone-related incidents that were the subject of education department disciplinary reports. In several of the incidents, which occurred during the 2005-06 school year, cell phones were at the center of violent struggles between teachers and students.

Teachers who tried to confiscate cell phones from students were met with a variety of unruly responses that ranged from “Chill yo, I’m doing something,”to shouting and violence, according to the write-ups.

In a March episode, a student in Brooklyn threw her phone at the teacher of her independent reading class after she was asked to hand it over. In April, in a school in Manhattan, a male student lunged at an administrator who had been called to a class to help a teacher confiscate a cell phone from a student.

The “occurrence reports,” as the education department calls them, are heavily redacted. The schools, the students, and the teachers involved in the incidents are not identified in the copies filed with the judge, Lewis Stone of state Supreme Court in Manhattan.

In addition, the education department for the first time provided a list of the types of cell phone disturbances at schools in the last school year. There were 581 reports of stolen cell phones through the first eight months of the year. During the same time period, phones were involved in 16 reports of sexual harassment and more than 300 reports of bullying and fights. In all, cell phones were involved in 2,168 separate school incidents, according to the data.

In several of the instances, it appears that the cameras that many cell phone models now feature were the cause of incidents. At a school in southwest Brooklyn in March, a male student used his camera phone to photograph an English exam. In January, a male student in Manhattan showed a picture of his genitalia to a female school aide, according to an incident report. In a neighboring school district, a gym teacher reported hearing rumors that two male students were taking inappropriate photos of themselves while at school.

The lawyer for the parents who are challenging the policy, Norman Siegel, said the incident reports the city has put forward prove little.

“In some of the instances they claim are problematic the cell phone was peripheral,” Mr. Siegel said. “We will always have some behavioral problems, but there are ways of dealing with behavioral problems short of an absolute ban on phones.”

Opponents of the ban say cell phones allow students to maintain contact with their parents in the event of an emergency.

Although the city ban against cell phones dates back to a 1988 rule forbidding pagers and other electronic items, the issue flared up this year when the schools began confiscating large numbers of cell phones.