Principal Teresa Vibar weaves through a crowd of students as classes change at St. Paul's Ramsey Middle School. She reaches out a hand to defuse an argument, and guides a scowling student to class.

There's shouting and jostling. Tension builds but doesn't boil over. It's a different atmosphere than Vibar found when she started as Ramsey principal in 2014 when student violence sparked complaints from parents.

"It felt — I'll be honest, it felt chaotic," Vibar recalled.

Extra district staff and some changes like no backpacks in the hallway helped quiet things down at Ramsey. But elsewhere in the district, high-profile incidents drew attention to school discipline. In one case a student at Harding High School was discovered to have a gun. A few weeks later at Central High School, a student choked a teacher unconscious.

The St. Paul teachers union went so far as to take the first move toward a strike because of perceived inaction by the district on school climate. As part of the contract St. Paul Public School teachers are negotiating, the union is asking for more district action on student misbehavior.

Still, there was no spike in one of measure of school violence — the number of fourth-degree assaults on school officials. The city of St. Paul's 2015 total is well within the range of the past 10 years.

District officials do have a plan. Some schools started using a strategy called Positive Behavior Interventions and Supports several years ago.

The model takes a preventative approach and aims to help students work out their own problems. It went district-wide last year. The change aimed to fix racial disparities in suspension rates, but so far those disparities still exist. The district also sent extra administrators to some schools, ramped up mental health supports, and expanded an alternative school that takes in some chronically misbehaving students.

But some teachers say the policies aren't working.

The district is so reluctant to punish students it has also stopped caring about small infractions like swearing or offensive T-shirt slogans, said Como Park High School teacher Roy Magnuson. Low-level misbehavior often snowballs into something larger, he added.

"Students are acting pretty much the way you would expect if they don't think anything is going to happen no matter what they do," Magnuson said.

The union, for its part, supports the less punitive approach to discipline. But it says schools need to staff up in order to improve conditions for teachers and students. One of its proposals calls for more counselors, social workers and other staff. So far that demand has been a sticking point as contract negotiations continue.

Johnson High School Principal Micheal Thompson says he could use extra staff — the school lost a behavior specialist this year, and there's been an uptick in fights. But Thompson says lots of external factors drive that spike too.

I think there's more and more trauma and crisis in some of the communities that the kids are coming from in our school," Thompson said.

Students' obsession with sharing video on social media can actually cause some fights, he added.

"They actually will set it up to film it — 'This is all arranged because we're going to film this. We already worked this out,'" he said.

The district says it's taking teachers' concerns into account. But officials insist the Positive Behavior Interventions model takes time. The district presented an updated discipline plan at last month's school board meeting.

The plan sticks to the Positive Behavior Interventions model but promises more student supervision and teacher training. It doesn't have much detail on how or when those additions will be implemented. That caused one board member to demand a timeline. A district official says that timeline will be presented at this month's board meeting.

Helping students solve their own problems means waiting to punish when arguments break out, said Kristy Pierce, a behavior specialist at Como Park High.

"You argue with family, you argue with friends and you don't get sent out in handcuffs," she said. "What we do is really try to teach kids to problem-solve and communicate effectively, which doesn't result necessarily in suspension."