Sousa Middle School Principal Dwan Jordon perched on the roof of the red-brick school Tuesday morning and hollered greetings to his students as they arrived.

Jordon, who was brought in three years ago to turn the troubled Southeast Washington school around, had a promise to keep.

“I’m on the roof because you’ve achieved our goal of 145 ‘Peace Days,’ ” he announced over the PA system as the school day began at 8:45 a.m. “I’m happy to be here, to be getting a couple of shades darker for you today.”

Principals at many schools use similar stunts to reward high test scores or good attendance. But for Sousa — a school with many students from neighborhoods where violence, drugs and gang activity are not uncommon — days with no in-school fighting are cause for celebration. Tuesday was Sousa’s 151st “Peace Day” in the roughly 180-day school year, with four days remaining.

Three years ago, Sousa was considered one of the District’s worst public schools. Labeled an “academic sinkhole” and a “dumping ground” for burned-out teachers, Sousa was portrayed in the 2010 documentary “Waiting for Superman” as a place toxic with low expectations and low test scores. Jordon said he was told that before he started, there were fights nearly every day, and students spent more time in the hallways than in class.

When then-D.C. Schools Chancellor Michelle A. Rhee appointed Jordon to take over in 2008, only 23 percent of Sousa students were proficient in reading and 17 percent in math.

Jordon fired most of his staff in his first year, and his new team focused on academics, mapping out detailed lesson plans and studying test score data. Test scores rose, but the principal wanted more.

“My first year, I knew I needed to improve student achievement quickly. We didn’t have one party; we didn’t have a lot of fun activities,” he said. “After that year, I realized, okay, let’s make this less about passing the test and make this a real school environment, the type of environment these kids deserve.”

Jordon and his staff encourage fairness and good citizenship by handing out Cobra Bucks — 30 earn a student lunch with the principal at Ben’s Chili Bowl. And students are taught, “when trouble finds you, find the nearest adult.”

“I’m more focused on building a better school environment, a place where kids feel safe and love coming to school,” Jordon said. “I’m always looking for possible signs, for kids who might have a tight face, kids who might be frowning.”

Jordan Reaves, 13, an eighth-grader who says she wants to be a dancer or a lawyer, said the school has changed since she was in sixth grade.

“We’ve been calmer this year compared to past years. We’ve been getting better over the years because of Mr. Jordon. He believes in us,” she said.

Reaves, who Jordon said was a straight-A student, said seeing her school depicted in “Waiting for Superman” in December pushed her to work harder.

“It showed me how people really thought of us — they called us the sinkhole,” Reaves said of the documentary. “If Mr. Jordon never came, test scores would still be low; he motivated us when we thought we were just Southeast kids.”

Jordon, who told the students that he would reward their good behavior by spending a day on the roof, climbed the narrow, winding staircase about 8 a.m. He had a desk, a laptop and two BlackBerrys.

As buses rolled in about 8, the students looked up as they headed to class. He promised he would stay until the school day ended.

“Aw, you okay up there?” a student asked.

“You’re gonna be burning up there today,” another said. (The students couldn’t see his cooler packed with ice and enough water and Gatorade to fuel a basketball team.)

Jordon greeted the students by name, calling out hellos and joking with some.

“Speed it up, Denise, speed it up,” he called out to a straggler trudging in late.