To the president of the St. Paul Federation of Teachers — and the union's 3,800 members — the issue of school safety is important enough to call a strike.

"Ask yourself this," said Denise Rodriguez, who has led the union for the past year and a half. "Do students and staff deserve to come to work every day and not expect to be assaulted? … Teachers want to know who has our back with this violence."

The assault last week of a beloved teacher at St. Paul Central has shocked parents, galvanized the union, rattled administrators and is raising troubling questions about student discipline and safety in the St. Paul Public Schools — questions that have plagued the district for the past couple of years.

But, while teachers increasingly talk about being shoved, punched and threatened by students in what they call an escalating hostile environment, no one seems to be able to quantify just how often teachers in the metro area, or elsewhere in Minnesota, are assaulted by those they teach.

This week, Ramsey County Attorney John Choi revealed data that give a local glimpse, saying his office has seen an alarming increase in cases of student-on-staff school violence. Choi said that the Central case was the 27th presented to his office this year under a gross misdemeanor statute that protects school officials from being assaulted or harmed. Cases have almost doubled in the past year, he said, and are up 60 percent over the previous five-year average.

While St. Paul and other school districts across the state annually track how many times students are disciplined for assault, weapons, threats, bullying and theft, they don't record those cases where teachers or school staff members were victims. According to data collected by the state Department of Education, there were 3,869 assaults reported in Minnesota schools in 2014-15, including 257 in St. Paul.

According to incident data from the St. Paul Police Department, police were called to public schools 118 times for assaults from Jan. 1 through the end of October this year. Over that same period, police were called 30 times for disturbances and fights and 26 times for weapons.

Unknown is how many incidents involved students against teachers.

Denise Specht, president of Education Minnesota since 2013, said school safety has become a major issue statewide.

"There are a lot of angry, traumatized, desperate students out there who don't know how to control their emotions. And when they lash out, teachers are often the first responders," she said.

Every teacher, she said, either has had a physical confrontation with a student "or has a colleague" who has, prompting statewide calls for increased training and resources for teachers. At its fall professional conference, Education Minnesota offered 19 different classes to help teachers with such things as working with students with mental health issues.

"This is about the best learning environment," she said. "We want our students and staff to be safe."

St. Paul schools Superintendent Valeria Silva said she, too, wants safe city schools. But, at a Wednesday news conference, she seemed to question whether safety alone was the reason teachers have requested mediation.

In addition to calling for restorative justice practices being implemented across the district — a move she said she does not oppose — teachers also are seeking raises of 2.5 percent a year over two years. Taken altogether, the union's proposals would cost the school district "millions of dollars that we don't have," Silva said.

The teachers union is pitching a proposal to improve school climate by drawing upon the expertise of counselors, social workers, nurses and psychologists, and by putting schools in charge of efforts to turn around problem behavior. The district, eyeing what could be an expensive proposal, instead has offered to convene a committee to study the issue and develop a plan that is financially sustainable.

The most recent incident to thrust school safety into the spotlight occurred Friday, when a 55-year-old Central High School teacher was choked into unconsciousness after trying to break up a fight that started over an argument about football statistics. When the teacher intervened, a 16-year-old student allegedly picked up the teacher and slammed him into a table and chair, before slamming him to the floor. The teacher passed out for 10 to 20 seconds.

Steve Marchese is one of four new St. Paul school board members who will take seats in January after being swept into office, in part, because of teacher and student concerns about school safety and student discipline. "This is exactly the stuff that was out there in terms of issues," he said Wednesday. "What we are seeing at Central is part of a conversation that has been happening for a long time in the district."

Marchese, whose son was once in homeroom with the longtime teacher assaulted on Friday, said the time has come for school district leadership to "take a hard look at the climate in the schools."

He said Silva and the administration need to address safety as part of a holistic strategy, and that the restorative justice proposal put forward by teachers is a "conversation starter" and that questions of how much it will cost can be discussed later.

That said, however, Marchese said school safety needs to be part of the district's financial bottom line. Schools must be safe, he said, or families will leave.

"Every incident like this, every story like this, creates an opportunity for people to say, 'I am not going to send my child to the St. Paul Public Schools,' " he said. "These things need to be examined in a way that the district really understands what is at stake."

Silva agreed Wednesday that restorative justice programs proposed by teachers could be part of the solution. But she said she wants to roll it out over time, at fewer schools. She insisted she wants to work with the union.

"I am deeply committed to find a common ground between the district and the union for the well-being of our students," she said. "There is nothing more important to me."

Asked what could be done to immediately improve school safety, Silva said the issue is complex and problems are often hard to predict. The student who allegedly assaulted the teacher last week, she said, has not been in trouble before.

"If we could have one way to solve it, we would have solved it. Sometimes there is no way — as in what happened on Friday."

Jim Walsh • 651-925-5041