Facing mounting pressure from students and activists, Mayor Bill de Blasio announced a suite of reforms Thursday to limit lengthy suspensions, curtail student arrests, and train educators across the city in alternatives to strict disciplinary measures.

The reforms are among the mayor’s most aggressive efforts yet to address stark racial disparities that often ensnare students of color in the criminal justice system or at suspension centers to serve lengthy punishments.

Starting next school year, officials plan to limit most suspensions to 20 days ― down from a possible 180 days, with some exceptions for serious violence or weapons violations. Last school year, thousands of students ― the vast majority of them black and Hispanic ― were suspended for over 20 days, which research suggests can lead to passing fewer classes, increasing their risk of dropping out, and lowering the odds of graduating.

This year, city officials had already begun quietly dialing back lengthy suspensions while they studied ways of formally changing the discipline code, the manual that dictates what punishments students should receive for various infractions.

Changes to the discipline code, which will be open to public input at a series of hearings over the summer, will be paired with additional training. All middle and high schools will be expected to receive instruction in “restorative” approaches to student discipline over three years, a constellation of practices that favor peer mediation and conflict resolution over ejecting students from their regular schools or classes. Those trainings will come as the city adds over 200 social workers to city schools; about 85 of them are part of the effort to address students’ needs before they escalate into misbehavior or crisis, officials said.

“This is a moment of change,” said Mayor Bill de Blasio, who is running for president and has faced questions about school discipline on the campaign trail. “This is a moment where students are going to get the support they need to be their best selves. Teachers are going to get the tools they need to help a child, the whole child, when there’s a challenge or a problem.”

The mayor also touted a new agreement between the education and police departments, first reported by Chalkbeat, that would limit the use of arrests and summonses in schools for low-level offenses. Ninety percent of arrests and summonses in schools are of black or Hispanic students, a percentage that’s in excess of their representation within the system, where they make up just shy of 70 percent of students.

Discipline reform advocates hailed the changes as a major win. “These reforms are a huge step,” said Tanya Benavides, a coordinator with Organizing for Equity, a group that has held rallies and pushed to cap suspensions at 20 days. “This is an important victory in the fight to decriminalize NYC’s schools, and disrupt the school-to-prison pipeline.”

The mayor has declined to address some other demands such as eliminating metal detectors or removing police officials from city schools entirely. (About 5,000 school safety agents are stationed in schools across the city, and they answer to the police department not principals.) 

Some of the changes announced Thursday are likely to spark criticism among educators who have argued discipline reforms have taken away their authority to manage student behavior. Under de Blasio, suspensions have fallen by roughly one-third, and there is evidence that the shift has contributed to less orderly classrooms in some schools.

Michael Mulgrew, head of the city’s teacher union, has been critical of some of the city’s efforts to reduce suspensions — including a proposed ban on suspensions for K-2 students that was eventually dialed back. But on Thursday, he flanked the mayor and said he supports the latest efforts to improve teacher training.

“The problem I had over the years is a lot of the advocates were like, ‘there will be no suspensions, and we’ll just train everyone on bias,’” Mulgrew said in an interview. “You need a whole package, and it has to be proactive not reactive.”

As part of Thursday’s announcement, officials said 50 middle schools will join a collaboration between the union and education department designed to give schools more intensive support to adopt alternatives to suspensions.

But Mulgrew emphasized he will be keeping a close eye on the rollout of these new training efforts.

“I’m going to get very loud and pushy when things aren’t going right,” he said.

This story has been updated to reflect that the cap on suspensions is not absolute but limits those over 20 days.