It’s 2 p.m., about three hours before school ends, and Bronx Lab School’s youthful principal, Marc Sternberg, is late for an interview. He’s sorry, but he has to speak with a teenager and her mother, who have dropped by because they are unhappy that the eighth-grader has not been placed here for next year.

Meanwhile, a ninth-grader is on Mr. Sternberg’s telephone telling his mother that he has been wrongly accused of being disruptive in class. Then there is the problem with the delivery of a much-needed computer. The tower came, but what good is it without a monitor? Mr. Sternberg is asked to weigh in on whether the year-old high school should accept the faulty order. His decision: Yes, since it took months to receive the order in the first place.

When he is finally able to get away, an hour later, Mr. Sternberg fields three cell-phone calls during the interview. Every day, he said, “is a challenge.”

Still, Mr. Sternberg, 32, wouldn’t have it any other way. For more than eight years, he dreamed of being a public school principal. When, while working as an educational consultant, he heard that Schools Chancellor Joel Klein’s Board of Education was dissolving low performing schools and would support smaller alternatives, he jumped at the chance to run one of his own design.

“Teaching was always something I felt good at,” said Mr. Sternberg, who grew up in Baton Rouge, La., the youngest child of parents who once owned Maison Blanche, a Baton Rouge-based department-store chain. “And it was a way I could contribute uniquely. A principal is the principal teacher.”

The doors of Bronx Lab, located on the second floor of Evander Childs High School, on East Gun Hill Road in the Bronx, opened last fall. But it took Mr. Sternberg a year to formulate the mission and program of the high school, which is one of 30 schools in the autonomy zone, a brainchild of Mayor Bloomberg and Chancellor Klein.

Based on his own teaching experience, graduate work at Harvard’s Business School and School of Education, and advice from educators at other innovative programs like the Bronx Guild High School and Colorado’s Eagle Rock School, Mr. Sternberg has created a school that “expects a lot from our students, holds kids accountable for their performances, engages their parents as partners, and creates an instructional environment where learning doesn’t necessarily happen in a 40-by-40-foot room but is a gateway to the world,” he said.

“So the emphasis is on project-based instruction,” he continued. “We have a 75-minute period. You can’t teach a 75-minute period like a typical 45-minute period. It has to be students doing things and making something. That creation becomes the act of learning.”

One important way is learning through internships. Next year, the 10th-grade class will earn school credits through internships of their choice. Other Bronx Lab differences: Ninth-graders learn algebra in conjunction with physics, field trips twice a month bring the world into the classroom, and the school day runs from 8:45 a.m. to 4:40 p.m.

So parents, think twice about enrolling your child here, warned Mr. Sternberg. “There is more of a burden on our students than the typical student to be an instigator of learning. Learning is an active, not passive, act.” In addition, parents must be involved in their children’s education. “We have monthly parent meetings, and there are lots of calls to and from parents,” he explained.

Mr. Sternberg has always known he wanted to help others. The passion was sustained, in part, by his time at Princeton, from which he graduated in 1995 with a bachelor’s degree in politics.

“I wrote my senior thesis on an episode of the civil-rights movement in Baton Rouge that was underappreciated, a bus boycott that predated Montgomery,” he said. “It became a study of the movement and leadership, and why leaders failed and succeeded.”

The idea of leadership would haunt him even as he spent the next three years teaching in a Bronx middle school, the first two as a Teach for America fellow. It came up again when, after his teaching stint, he had to decide between rabbinical school and business school.

“It was really about leadership and equipping myself with the tools to make a contribution,” said Mr. Sternberg, who lives with his wife, an assistant district attorney, in upper Manhattan. “I would argue that it shouldn’t matter if I had an MBA or a rabbinic degree; the idea is still the same. It was fueled by the same passion.”

With parental encouragement, he ultimately opted for Harvard Business School. Exposure to management ideas and lessons about visionary leaders further fueled his desire to address issues of poverty and equity. He graduated with an M.B.A. in 2000 and a master’s from the School of Education in 2001 and returned to work as a consultant for Victory Schools, a charter school management company.

Then, in the summer of 2003, he received a call from the Bronx deputy superintendent about a job as a principal. The conversation rekindled his desire to help people in a more immediate, personal way. He started to research and craft the idea for Bronx Lab.

Being in charge of 100 mostly minority teens, with another 100 coming in next year, has certainly gotten Mr. Sternberg deeply involved. He says one of the challenges – and joys – of the job is “the level of involvement in our student’s personal lives. When a student runs away from home or has an unexpected pregnancy or whatever, we are part of their families and they are a part of ours.”

Another challenge that he and the 11 other handpicked educators and administrators contend with is the differing abilities of their pupils. “Some are terrific students who know how to learn and think; they are a pleasure to be with,” he said. “Others are still a pleasure to be with, but their level of competency and the skills we are teaching are radically different. How do you deal with a classroom of 20 students when some are here and others are here and make that a meaningful experience for everyone and a fulfilling experience for the educator?”

While next year will bring to life a major component of the Bronx Lab curriculum – the internships – Mr. Sternberg and his team are already preparing for a future when the school will have a student body of 400 and go from ninth to 12th grades. They are drafting plans for a summer program and an athletic program.

The aim: “to make Bronx Lab School a premier high school in the Bronx,” he said.

It’s a tall order since money is in short supply. “We get $8,000 per pupil, but go 15 miles north in Westchester, and they get $12,000 per pupil,” said Mr. Sternberg. (Bronx Lab receives most of its funding from the city, but also landed a $400,000 four-year grant from the Bill & Melinda Gates Foundation.) “We need hundreds of thousands of dollars, but then you always need more.”

It’ll take years to accomplish, but Mr. Sternberg said he’s in it for the long haul.