Fresh out of college, Michelle A. Rhee joined Teach for America, the fast-track teacher training program, landing at Harlem Park Community School in Baltimore. The public school ranked near the bottom in city reading and math scores, and as a new teacher, Ms. Rhee got a classroom of 35 children achieving the worst and behaving the worst.

"They ran right over me," Ms. Rhee recalled. She ended that first year "convinced that I was not going to let 8-year-olds ruin my life."

The next fall she combined classes with another teacher, and together they taught the same children for two years. By the end of the second year, she said, the class that had been testing in the 13th percentile was on grade level, with some children soaring to the 90th percentile.

Now, Ms. Rhee is betting she can replicate that success on a citywide scale as the newly named chancellor of schools in Washington, arguably the nation's most dysfunctional school system. Though it is one of the country's highest-spending districts, most of the money goes to central administration, not to classrooms, according to a recent series of articles in The Washington Post. Its 55,000 mostly poor students score far worse than comparable children anywhere else in reading and math, with nearly 74 percent of the district's low-income eighth graders lacking basic math skills, compared with the national average of 49 percent.

"I just want to get to work," said Ms. Rhee, whose appointment depends on approval by the City Council and who is now technically acting chancellor. She was tucked away in a cramped computer room at the New Teacher Project, a nonprofit group in New York City that she founded in 1997, when she was 27, and still runs.

The project trains midcareer professionals to become classroom teachers. Since its founding, it has trained and supplied 23,000 teachers to urban districts nationwide. It recruits and hires teachers to work in four of the eight largest school systems: New York City, Chicago, Miami and Philadelphia.

A graduate of Cornell University with a master's from the Kennedy School of Government at Harvard, Ms. Rhee speaks directly and confidently. On measuring her success, she said, "We're going to significantly raise student achievement levels, and we're going to close the achievement gap."

Not narrow the gap, but close it.

"I see a clear path to getting it done," she added.

Her appointment was the first act of Washington's new mayor, Adrian M. Fenty, upon his formal takeover of the public schools last week, and the criticism was quick in coming.

Some school officials, City Council members and parents complained that in naming Ms. Rhee, Mr. Fenty had failed to consult enough with parents and teachers. But other criticism focused on Ms. Rhee herself.

Ms. Rhee, 37, a Korean-American, will be the first schools chief in 40 years who is not black. In Washington, 95 percent of the district's public school students are black.

And Ms. Rhee has never run a school or a school system before. Not even a little one.

But she seems undaunted by the criticism and the challenges ahead, pointing out that through the teacher project, she has volumes of experience with many largely minority, urban systems. Sitting down recently with parents and community leaders, Ms. Rhee recalled, she looked around the room and said: "I know what you're all thinking. What's this Korean lady doing here?"