At Explore Charter School, a Portrait of Segregated Education IN seventh-grade English class, sun leaked in through the windows. Horns bleated outside. The assignment was for the arrayed students to identify a turning point in their lives. Was it positive or negative? They hunched over and wrote fervidly. Floriande Augustin, a first-year teacher at the school, invited students to share their choices. Hands waved for attention. One girl said it was when she got a cat, though she was unsure why. Another selected a car crash. A third brought up the time when her cousin got shot and "it was positive because he felt his life was crazy and he went to college so he couldn't get shot anymore." The lesson detoured into Martin Luther King Jr. and his turning points. Ms. Augustin listed things like how his father took him shopping for shoes and they were made to wait in the back. How a bus driver told him to relinquish his seat to a white passenger and stand in the rear. How he wasn't allowed to play with his white friends once he started school, because he went to a black school and his white friends went to a white school. The students scribbled notes. Unmentioned was a ticklish incongruity that hung glaringly obvious in the air. This classroom at Explore Charter School in Flatbush, Brooklyn, was full of black students in a school almost entirely full of black students. As Ms. Augustin, who is also black, later reflected, "There was something about, "Huh, here we are talking about that and look at us - we're all the same." " In the broad resegregation of the nation's schools that has transpired over recent decades, New York's public-school system looms as one of the most segregated. While the city's public-school population looks diverse - 40.3 percent Hispanic, 32 percent black, 14.9 percent white and 13.7 percent Asian - many of its schools are nothing of the sort. About 650 of the nearly 1,700 schools in the system have populations that are 70 percent a single race, a New York Times analysis of schools data for the 2009-10 school year found; more than half the city's schools are at least 90 percent black and Hispanic. Explore Charter is one of them: of the school's 502 students from kindergarten through eighth grade this school year, 92.7 percent are black, 5.7 percent are Hispanic, and a scattering are of mixed race. None are white or Asian. There is a good deal of cultural diversity, with students, for instance, of Haitian, Guyanese and Nigerian heritage. But not of class. Nearly 80 percent of the students qualify for subsidized lunch, a mark of poverty. The school's makeup is in line with charter schools nationally, which are over all less integrated than traditional public schools. At Explore, as at many schools in New York City, children trundle from segregated neighborhoods to segregated schools, living a hermetic reality. The school's enrollment is even more racially lopsided than its catchment area. Students are chosen by lottery, with preference given to District 17, its community school district, which encompasses neighborhoods like Flatbush, East Flatbush, Crown Heights and Farragut. Census data for District 17 put the kindergarten-through-eighth-grade population at 75 percent black, 13 percent Hispanic, 12 percent white and 1 percent Asian. But the white students go elsewhere - many to yeshivas or other private schools. Tim Thomas, a fund-raiser who is white and lives in Flatbush, writes a blog called The Q at Parkside, about the neighborhood. He has spoken to white parents trying to comprehend why the local schools aren't more integrated, even as white people move in. "They say things like they don't want to be guinea pigs," he said. "The other day, one said, "I don't want to be the only drop of cream in the coffee." " Decades of academic studies point to the corroding effects of segregation on students, especially minorities, both in diminished academic performance and in the failure to equip them for the interracial world that awaits them. "The preponderance of evidence shows that attending schools that are diverse has positive effects on children throughout the grades, and it grows over time," said Roslyn Mickelson, a professor of sociology and public policy at the University of North Carolina at Charlotte, who has reviewed hundreds of studies of integrated schooling. "To put it another way, the problems of segregation are accentuated over time," she said. Even if a segregated school provides a solid education, studies suggest, students are at a disadvantage. What is a good education? Dr. Mickelson said. That you scored well on a test? One way race presents itself at Explore is in the makeup of the teaching staff. It is 61 percent white and 35 percent black, a sensitive subject among many students and parents who would prefer more black teachers. Most of the administration and central staff members - including the school's founder, the current principal, the upper-school's academic head and the lower-school's academic head, as well as the high school counselor and social worker - are white. As Ms. Augustin said: "When I came here and started to talk about myself, the students were shocked that I was here. I started to wonder, did they really have role models? AFTER school one Tuesday, 10 students assembled in a classroom to talk about the school and race. The school paid for snacks: Doritos and Oreo cookies, Coke and 7Up. What did they think of the absence of racial diversity? "It doesn't really prepare us for the real world," said Tori Williams, an eighth grader. You see one race, and you're going to be accustomed to one race.