"The reason they are not accurate is that people are being discouraged from reporting," said Ted Kirsch, president of the union.

He said the union was looking into reports that teachers at one West Philadelphia elementary school must obtain permission from school officials to fill out a discipline slip. "You can't do that," he said.

Kirsch blamed what he perceived as a rise in assaults and disruption on a decrease in nonteaching assistants in the schools.

Two years ago, union records show, the district had 406 nonteaching assistants who helped with discipline and security, monitored hallways, and helped teachers handle problems in classrooms. Their ranks have shrunk to 242. Many teachers say that when they step into the hallway to look for help, no one's there.

Although the district has hired community groups to help in the schools, the union maintains they work part time and lack the training and experience of the nonteaching assistants.

West Philadelphia High School, which has reported the most incidents this year for a school its size, had six or seven nonteaching assistants a few years ago, said Vi Curry, the teachers' union representative who works with staff in the building.

This year there are three.

Ron Dillard, a nonteaching assistant who was assaulted there Wednesday, was substituting for an assistant out on disability for an assault.

On Friday, when three students were arrested on allegations they punched another West Philadelphia teacher in the face, sophomore Aisha Matthews said she felt for the teachers.

"It's hard for them to teach. They feel unsafe," Matthews, 16, said. "They need more , more cops. "

And parents worry about their children.

"My mom feels that I shouldn't have to come to a school where I don't feel safe. I should be at school to learn," Matthews said.

Vallas pointed out that he had doubled the number of school personnel aiding school security since 2002.

He's using more parent volunteers, parent truancy officers, "climate managers," and other employees - and fewer unionized nonteaching assistants.

Safety and violence prevention have been a cornerstone of Vallas' administration and yet remain, perhaps, his biggest frustration.

Within two months of his arrival in July 2002, he announced a "zero tolerance" crackdown on violence and disruption in the schools and threatened to fire principals who failed to report incidents. The policy, embraced by the union and parents, led to a large increase in reported incidents in the 2002-03 school year.

But it was no panacea.

Problems persisted: Shootings outside schools that claimed the lives of students. Large-scale fights in the big neighborhood high schools. Loaded guns found in lockers and hallways. A rape committed by a middle school youngster while classes went on around him. A kindergartner who punched a pregnant teacher in the stomach.

Each major incident prompted a new reaction from Vallas.