Jallon Brown is barely 30 years old, but already has had a notable career in education.

After graduating with a full load of teaching courses from the College of William and Mary in 1996, she showed such skill in classrooms in Williamsburg, Va., and Silver Spring that by age 27 she was working as a full-time mentor teacher, spending all her time helping other teachers get better.

Last year she applied to the Knowledge Is Power Program (KIPP), a national nonprofit organization that trains outstanding educators to open and run high-performing public schools. She was among 11 out of 250 applicants accepted to the KIPP School Leadership Program, a demanding year-long course of study beginning at the Haas School of Business at the University of California-Berkeley. Brown also has a master's degree in educational administration from George Washington University.

Now, in what she says will be the greatest challenge of her young life, Brown has been named principal of the KIPP Harbor Academy, a proposed new middle school in Annapolis that would become the second public charter school in the Washington suburbs. Charter schools use tax dollars but are free of many district regulations under a new law in Maryland.

"Annapolis is the capital of Maryland and I think it is a great opportunity to bring a charter school to the capital and to create a new kind of opportunity for its students," she said.

It is unusual for someone Brown's age to be starting a new school, but San Francisco-based KIPP is known for giving heavy responsibilities to very young and determined educators.

KIPP founders Mike Feinberg and Dave Levin were 25 and 24 when they started their first school in Houston in 1994. They had met two years before, when Feinberg graduated from the University of Pennsylvania, Levin graduated from Yale and they joined the Teach For America program to teach in the inner city.

They said they were terrible during their first year in elementary school classrooms full of low-income children, but worked hard to improve and decided by the end of their second year they knew enough to start their own program. They used a series of chants, games and other devices taught to them by Harriett Ball, a successful veteran teacher in Houston, and added a longer school day, an absolute insistence on homework completion and regular excursions that provided what they called a necessary "joy factor."

Their success, both at the original Houston school and at a second school Levin started in the South Bronx, led to an appearance on the television show "60 Minutes" and a major investment by Doris and Donald Fisher, founders of Gap Inc., to begin training principals for more KIPP schools.

There are now 36 KIPP middle schools, plus an elementary school and a high school, in 13 states and the District. Brown's KIPP Harbor Academy, if approved by the Anne Arundel County Board of Education, would be one of nine schools KIPP hopes to open next summer. More than 80 percent of KIPP students are from low-income families, and yet their test scores in many cities rival those of students with affluent, college-educated parents.

The KIPP DC: KEY Academy in Southeast Washington has the highest math scores in that city, and reading scores that are bested only by two schools with mostly middle-class students in Northwest Washington. Susan Schaeffler started the KEY Academy in 2001 when she was 31. One of her original teachers, Khala Johnson, now 32, has been selected to start a second KIPP school in the District next summer.

Brown originally planned to open a second KIPP school in Baltimore this year, following the success of the KIPP Ujima Village Academy, which has the highest sixth-grade math scores in Baltimore. When those plans were delayed, she responded to a request from Annapolis community leaders who were interested in a KIPP school.

Brown said if the school is approved as she hopes by December, she will begin selecting teachers. She plans to interview and observe teaching candidates in a classroom before hiring. The Harbor Academy would begin with a fifth grade of about 80 students, and would add a new grade each year until it becomes a fifth-to-eighth-grade school of about 320 students.

The Annapolis school would be one of seven KIPP schools employing unionized teachers. Brown said she is looking forward to a partnership with the Teachers Association of Anne Arundel County. KIPP teachers are typically paid about 15 to 20 percent more than regular school staffers because of their longer school day, which usually runs from 7:30 a.m. to 5 p.m.

Education experts say they are impressed by KIPP's results, but want to see if they hold up over time in new schools such as the Harbor Academy.

Brown said the longer school day is a key to the success she hopes to achieve. "Teachers often say to themselves, 'If I could only have one more hour each day,' " Brown said. "Well, we give them that, and more."