Already this school year, two of her students have been shot dead, including a 16-year-old killed last week. The area has more homeless shelters than any other part of the city. For generations, the local school districts she now runs were marred by racial strife and corruption.
Yet in the last three years, Dr. Cashin has produced one of the school system's most unlikely success stories. Since 2003, her elementary and middle schools have consistently posted the best total gains on annual reading and math tests, outpacing other regions with similar legacies of low achievement.
''It's not a job, it's a lifework,'' she often tells her staff. ''You are saving children's lives.''
Dr. Cashin's results should be an easy reason for Mayor Michael R. Bloomberg and Schools Chancellor Joel I. Klein to gloat, a triumph in their takeover of the nation's largest school system. But in many ways, her success raises questions about the thrust of their recent efforts to reshape the school bureaucracy.
While Mr. Klein has derided the ''status quo crowd'' and sought to bring outsiders into the administration, Dr. Cashin is a lifelong city educator. While Mr. Klein wants to free principals from the control of superintendents like her, Dr. Cashin believes even the best principals need an experienced supervisor.
Where Mr. Klein insists that school administration must be reinvented to reverse generations of failure by generations of educators, Dr. Cashin, a product of the old system, insists she can get results with a clear instructional mission, careful organization and a simple strategy of every educator's being supported by an educator with more experience.
In short, Dr. Cashin stands, in a way, as the antithesis of Mr. Klein's mission to slash midlevel bureaucracy and let principals sail on their own, a challenge to the notion that changing governance structure is the key to turning around schools.
She runs her schools in Region 5, with more than 85,000 students, the same way she ran her schools under the old Board of Education and under previous mayors.
The tug and push over how to manage the system is not academic. Across the country, big school districts have looked outside the ranks of educators, turning to experts in business, law or the military for help. Mr. Klein is a lawyer; Los Angeles hired a retired Navy admiral; the Seattle superintendent is a former banker and public utilities official.
But with studies showing little progress in narrowing the achievement gap between minority and white students, the question of how best to improve schools in places like Region 5 is the most critical issue in American education. And Dr. Cashin has the numbers to stake a claim as the best turnaround artist in town.
In 2003, 33.2 percent of her students in grades three to eight could read on grade level and 34.6 percent were proficient in math. Today, 50.6 percent read on grade and 56.9 percent are proficient in math. No other region starting below 40 percent has crossed the halfway mark in either subject.
''We are relentless,'' Dr. Cashin said in a recent interview. ''The secret is clear expectations. Everything is spelled out. Nothing is assumed.'' She provides her principals, for instance, with a detailed road map of what should be taught in every subject, in every grade, including specific skills of the week in reading and focus on a genre of literature every month.
Dr. Cashin was chosen by Mr. Klein to be one of 10 regional superintendents, as part of the initial restructuring of the city's 32 local school districts under Mr. Bloomberg's control of the system. But since the start of the mayor's second term, Mr. Klein has pushed to reduce the role of superintendents, giving wider authority to principals in an effort that could lead to consolidation or elimination of the 10 regions. That could potentially leave the regional superintendents without jobs or perhaps filling a new role in which principals choose them to advise groups of schools. They would no longer be supervisors but rather support staff.
In a statement, Mr. Klein praised her for doing a ''terrific job.'' But, through a spokesman, he suggested that Dr. Cashin was one of few exceptions to come up through the ranks and that Region 5's results, while impressive, were still incremental, while he wants much larger citywide improvement. He also reiterated his intention to ''devolve decision making and resources'' to give principals more power.
In an interview, Andres Alonso, the deputy chancellor for teaching and learning, also suggested that Dr. Cashin and Mr. Klein were not so different. ''She has a huge entrepreneurial side,'' he said. But he tempered his praise, noting that aggregate improvements in scores, across many grade levels, can mask slower progress in particular areas.
He also said the mayor's initial restructuring had set the stage for her region's gains. ''They were given the span of control, they were given the political authority, they were given the resources,'' he said of the superintendents. ''They were supported comprehensively.''
Dr. Cashin, a Brooklyn native who once studied to be a nun and now zips through some of the city's bleakest quarters in a dark Lexus, does not criticize her bosses publicly. But just 15 of 115 principals in Region 5 joined the chancellor's ''empowerment'' program, which frees principals from answering to superintendents in exchange for their agreeing to meet performance targets. Other similarly sized regions had two or three times as many sign up.
Dr. Cashin prefers principals who come up through the system over graduates of the chancellor's Leadership Academy, which has focused on recruiting candidates from other professions. And while Mr. Klein has dealt with the teachers' union on a war footing, Dr. Cashin has made the union a partner, hiring it to train teachers instead of using outside vendors.
Though she uses the citywide math and reading programs in many schools, Dr. Cashin does not believe they are sufficient and customizes them extensively, with an emphasis on writing. She also uses an array of other initiatives of her own choosing or design.
''You need to expand the knowledge base, expand the vocabulary, expand the experience base, and that only comes with good instruction and a rich curriculum,'' she said.
In Region 5, about 100 principals are overseen by 13 local instructional superintendents, who are constantly in schools to make sure they are on track and who meet weekly with Dr. Cashin and her longtime deputy, Stephen M. Mittman.
Close associates of Dr. Cashin, who turns 59 this month, said frustrations with headquarters at times had prompted her to consider retiring. But she is divorced, with three stepsons but no children of her own, a regret she describes as ''an emptiness in my heart.'' So far, her friends said, she cannot bring herself to give up her life's work.
Dr. Cashin grew up in Flatbush, the youngest of five children. Her parents died when she was a teenager. She studied to become a nun but settled on teaching, first in Roman Catholic school and then at Public School 299 in Bushwick until teacher layoffs in 1976.
She worked in educational publishing, then in curriculum development for the Board of Education. In 1982, she became principal of P.S. 193 in Midwood, where she stayed until becoming superintendent of District 23 in Ocean Hill-Brownsville, the epicenter of battles between black parents and white educators in the 1960s.
Former Chancellor Rudy Crew, who hired her for District 23, said Dr. Cashin excelled in the technical aspects of teaching: ''She is a principal's dream.''
To appoint her, Dr. Crew overruled neighborhood opponents who were demanding a black superintendent and branded her ''the white lady from Bensonhurst.'' (She is from Bay Ridge.)
Denise Gordon, a longtime parent organizer, said Dr. Cashin bridged racial divisions. ''I tell everyone she's tan because she's black underneath,'' said Ms. Gordon, who is black.
These days, Dr. Cashin, who is 6 feet tall with short blond hair, strides into schools, juggling her cellphone and BlackBerry, doling out hugs to parents, kisses to principals and a never-ending stream of thank-yous to her teachers. She calls everyone Baby or Hon.
''You have to be kind to people,'' she said. ''If people feel they don't have a voice, they are going to strike back at some point.''
Although Dr. Cashin is beloved by parent and community groups, often impressing them with her passion for children, some who have worked with her say that she can be imperious, that she listens intently but can be difficult to persuade to change her mind.
She is often generous with praise, but her criticism can be merciless. ''It's got to be much more rigorous,'' she told a principal after touring a Brownsville elementary school. Her quiet tone did not mask her fury. ''I don't think there's a sense of urgency.''
She was particularly distressed to see some children sharing books and noted with disdain that some were doing busywork. ''I saw, in one or two rooms, copying from the board,'' she said, derisively. ''I don't know what that was all about.''
Dr. Cashin is obsessed with writing, and in most of her schools, student work lines the walls -- not just the final product but layers of drafts. Even first graders have writing posted on the walls.
A feature used in every school is the four-square graphic organizer, a worksheet with four boxes like a window pane and a rectangle at its center that helps children develop a five-paragraph essay. Some progressive educators scorn it as a crutch; Dr. Cashin insists that it works.
While the city's reading program focuses on story books, Dr. Cashin layers on lots of nonfiction. And, responding to research showing that impoverished children often lack vocabulary and basic facts, she has adopted a curriculum called Core Knowledge, which teaches basics like the principles of constitutional government, events in world history and well-known literature.
''The question to raise is, why aren't more schools doing this?'' said Pedro Noguera, an education professor at New York University. ''Why aren't more of these approaches that are proven to be effective being adopted more widely in the city?''
Others say they are impressed by her organization. ''They stick with a plan, make sure the resources get to the plan and follow up to see if the plan worked,'' said Seppy Basili, the vice president of Kaplan K12 Learning Services, the test preparation company, who has worked in districts nationwide.
While the scores in Region 5 reflect extensive test preparation, on that front, too, Dr. Cashin does things her way, having pushed Kaplan to develop a program to her specifications.
At a recent conference on homeless children, Dr. Cashin recalled the anxiety among some of her principals over an influx of students from a shelter. ''The children from the Junius Shelter are going to be coming,'' she said, recalling the unease. ''What are we going to do? Our reading scores have just started to go up.''
''These are the children that are traumatized, that are hungry, that are fatigued, that are stressed,'' she told the audience.
''We decided the goal was not to try to
take the fewest numbers, but to have
T-shirts for them, and book bags and
intervention services, to welcome them, be
nurturing to them, because these are the
children who have been most hurt.''