Ninth-graders attend the opening of Ron Brown College Preparatory High School in Washington on Monday. (Marvin Joseph/The Washington Post)

Monday wasn’t just the first day of school for the 110 freshmen at Ron Brown College Preparatory High School in Northeast Washington. It was first day of school for the school itself.

The District’s newest high school, the only single-sex public high school in Washington, opened with a mid-morning ceremony punctuated by piped-in soft jazz and speeches from the mayor, the chancellor of the school district and D.C. Council members.

But even as the officials spoke, the teaching and learning was well under way. The students, wearing the school uniform — blue blazer, white shirt, purple-and-gold striped tie and khakis — began their day in gleaming new classrooms at 7:15 a.m., while most of Washington was still on its first cup of coffee.

Ben Williams, the school’s 36-year-old principal, woke up at 6 a.m. Monday. And at 5. And at 4. It was a sleepless night for a leader who has great expectations for his “young kings.”

Students enter Ron Brown College Preparatory High School as it opens its doors Monday. (Marvin Joseph/The Washington Post)

“Finally. It’s finally here,” Williams said Monday morning. “I want them to have a positive experience. I want them to feel that this is an environment where they feel welcome, where they can take chances and where they feel comfortable from day one being vulnerable.”

On the first day of classes for most public schools across the city, Williams said he saw pride in the faces of the young Ron Brown students as they “were starting to realize that this is their school.” In a brief speech to students, Williams noted that Ron Brown’s community has adopted a quote from W.E.B. Dubois as its motto: “Now is the accepted time, not tomorrow, not some more convenient season.”

The school opens with a class of ninth-graders. It will add a class each year so that when the current freshmen graduate in 2020, Ron Brown will have a full student body.

The school, in what used to be Ron Brown Middle School in the city’s Deanwood neighborhood, is in the middle of a $58 million phased renovation project that is completed on the lower floors and will continue on the upper floors. The capacity of the school is slated to be between 500 and 600 students by fall 2019.

Absalom Bolling, 14, is one of the school’s proud new students. He chose Ron Brown because he wanted to go to an all-boys school and is excited about the opportunities that await him. A “highly competitive” swimmer, Bolling is pushing to get a swim team started at the school. That’s just one of the many plans he’s making.

“I’m ready to hit the ground running,” he said. “I have a lot of goals. I plan to get a 4.0 and just do my best all the time and impress a lot of people.”

Later, Bolling introduced D.C. Mayor Muriel E. Bowser, a task he handled with a politician’s aplomb, welcoming her as the “mayor of the soon-to-be 51st state,” which drew a wide smile from Bowser.

The mayor said that the opening of the school was a historic day. The school, she told an audience that included D.C. Council Chairman Phil Mendelson and council member David Grosso, will get students “ready to be the fathers and young men that will lead our city forward.”

The creation of Ron Brown was a pet project of outgoing D.C. Schools Chancellor Kaya Henderson, who decided last year to invest $20 million in a city initiative for black and Latino boys, who make up 43 percent of the students enrolled in D.C. Public Schools and whose academic achievements have fallen short of other groups.

“This is a dream come true, and we will continue to defy expectations,” Henderson said at Monday’s opening ceremony.

The decision to have an all-boys public high school has drawn some criticism because there is not a similar high school for girls. But Bowser and Henderson both defended the school.

“We’re not a one-size-fits-all school district,” Henderson said, adding that the school system is looking at data about its girls and is exploring whether an all-girls school also would be a good idea.

Bowser spoke about the importance of meeting the needs of “all of our children” in D.C. Public Schools. “If you look over the District of Columbia, if we have a group of people that is very vulnerable, it’s boys and young men,” she said.

Charles Curtis, a psychologist on the school’s staff, said that one of the reasons he wanted to work there was to change the experience that many young men of color have in school.

“It’s often a springboard for negative outcomes for them,” Curtis said. “We want to change the narrative and create a space where we foster their greatness.”