Ronda Cooperstein wasn't surprised to hear of the assault on a teacher at the school where she used to work. The only difference between this one and those she saw was that it was captured on video - and drew nationwide media attention.

Until 2006, Cooperstein worked as the librarian for adjoining Reginald F. Lewis and W.E.B. Du Bois high schools, where a teacher's beating April 4 was recorded on a student's cell phone camera and aired last week on CNN and the Today show. During Cooperstein's three years at the schools and 20 years in the city school system, assaults on staff were a "chronic problem," she said. Three times, she was attacked.

"Believe me, this is not news to those of us who have worked in the schools," said Cooperstein, who resigned from the system last year. "It's a day-to-day problem, and if it doesn't happen to me today, it might happen to you tomorrow."

The assault on Jolita Berry, a new art teacher at Reginald Lewis High, has shined a light on what educators in the city school system say has been a problem for years. This academic year, school police have made about 50 arrests for staff assaults, and the system has expelled students 112 times for assaulting staff members. Officials couldn't say how many of those expelled also were arrested.

At this time last year, there were 98 expulsions for assaults on staff, but officials say the change might have been in reporting rather than incidents. Lack of reporting is a historic problem in the system, and city schools chief Andres Alonso has threatened to fire anyone who does not report violence.

Of the 112 incidents, 79 involved assaults on teachers; the rest were against administrators, school police officers and substitute teachers, according to the school system. Students hit, pushed or slammed doors on staff members. One teacher was bitten.

The incidents represent the most serious offenses, ones that led to a student's removal from a school for more than 45 days.

The state reported that Baltimore suspended students for attacking staff members 515 times last school year. That compares with 479 suspensions in Baltimore County, a larger system that has had troubles of its own in the past few weeks, including two instances in which guns were discovered at schools.

Jonathan T. Brice, the city school system's executive director of student support, said the state figure is a "broad, catch-all category that could mean that a student merely brushed past the teacher."

In the Reginald Lewis case, video footage shows a woman lying on the floor while a teenage girl beats her. On Thursday, as Berry was interviewed by Matt Lauer on Today, a student and teacher at Mergenthaler Vocational-Technical High were involved in a physical confrontation that left both hospitalized. That same day, a teacher at Dr. Samuel L. Banks High was hospitalized after a student hit her in the face with a textbook. Mervo had other problems Friday, closing early because of an arson.

Teacher assaults are part of a broader landscape of school violence that Alonso must confront as he goes about the process of reform.

Soon after arriving last July, Alonso directed principals to gauge whether their school communities would support the installation of metal detectors. Forty schools, including Lewis and Du Bois, requested the devices, which were recently installed.

Alonso said many schools lack the resources to adequately address violence that spills over from the neighborhoods they serve. Starting this summer, the system is overhauling the way it funds schools, giving more money to principals to spend at their discretion. That will allow schools to add anti-violence measures such as in-school suspension and mediation programs. The system is also working to expand mental health programs.

A key component of positive school climate is leadership, and Alonso has indicated that he will replace some principals this summer. He wants all schools to have community governing boards to increase volunteerism, and he is pushing peer mentoring and apprenticeships.

"These are the types of interventions that will eventually turn the system around," he wrote in an e-mail to The Sun.

Alonso is preparing to announce an overhaul of the way the city structures alternative schools, which serve many students who get expelled for violent behavior. Plans are also in the works for new alternative schools, because the city doesn't have enough space to meet demand. Alonso said the system must rethink the way it serves overage students, who are suspended in disproportionately high numbers.

As a result of the space shortage, students who are suspended for an act of violence are often sent back to the same school, and the cycle continues.

Jimmy Gittings, president of the city's administrators union, said he asked Alonso last week to stop that practice and to send the suspended students elsewhere.

At Doris M. Johnson High School in East Baltimore, Principal Tricia Rock refuses to take those students back.