Santos grew up in Queens in the ’80s, with the kind of childhood that makes it easy for him to empathize with the students in his school, 70 percent of whom qualify for free lunch and 80 percent of whom are students of color. His father was incarcerated for part of his childhood, and his mother, he says, was not stable enough at the time to care for a child. Instead he was raised by his great-grandmother, great-aunt and great-uncle. In high school, Santos became active in his youth church and considered becoming a pastor before switching to education. He is a trim man who carries himself with a brisk, military bearing. He intimately understands, he says, why so many of his male students feel compelled to fight to prove themselves. He was born with one hand and could have been a target. “If I went to a new school, if I didn’t fight early on, the rest of my time there would have been harder,” he says.

Santos arrived at Leadership, where most incoming students are performing below grade level, wanting to make changes, fast. At times, in his righteousness, he approached his staff as if he were taking on that first fight at a new school. “If you are unwilling to hold our students to high expectations,” he wrote in a newsletter to teachers early in his tenure, “provide the necessary support, restore damaged relationships and demonstrate unconditional love, then Leadership and Public Service is not for you.”

Leadership had long been the kind of school where many teachers saw their job solely as teaching; managing discipline was the role of deans, whom they would call to the classroom “for anything more than the crumpling of a paper,” says Sara Mitchell, a music teacher who started at Leadership two years before Santos. Santos’s priority was to shift that habit; he urged teachers to take the time to talk to the student, calmly, outside the classroom, to work on building the relationship — even to take responsibility for possibly inflaming a situation with a harsh tone of voice.

Many teachers decided that the school, under Santos, was not, in fact, for them. Eleven out of 51 left at the end of his first year. Some would have retired or moved anyway, but others were skeptical about his empathy-based approach. (“What are we, going to get in a circle and sing ‘Kumbaya’?” one was heard to mutter during a faculty meeting.) Some worried that Santos wanted to cede too much control to students, while others felt he wanted more work from them on their own time than was reasonable. “I think they felt, Are you saying I am not pushing myself enough already?” says Candace Thomas-Rennie, a guidance counselor at Leadership whom Santos hired in his first year as principal. “That’s insulting for a veteran who has the results to back up their own practice.”

Santos replaced the staff members who left with a diverse group of young teachers and recruited a new dean, Erin Dunlevy, a 32-year-old former Spanish teacher who had been trained in restorative practices. Before the school year even started, she spent a few hours one day introducing the principles of restorative justice to about 20 students who were chosen because they had leadership potential but also were often in conflicts. Dunlevy knew change would take time, but she was still rattled when, within the first month of school, one girl from that group brawled with another girl. Dunlevy, who tried to intervene, ended up in the emergency room with a broken toe, after a fire extinguisher that one girl threw at the other landed on her foot. “There was a lot of heavy lifting to do at that school,” Dunlevy says; later that year, a student fired a gun at a bathroom urinal. (That student and the girls who had fought were suspended.)

She continued to work closely with students as well as the other disciplinary deans, teaching them how to conduct circles that would resolve conflicts. The training emphasized each party involved owning up to his or her responsibility and making amends, with an honest conversation or an action (a student who had left a classroom in disarray might help the teacher clean it).