Enrollment in nearly half of the nation’s largest school districts has dropped steadily over the last five years, triggering school closures that have destabilized neighborhoods, caused layoffs of essential staff and concerns in many cities that the students who remain are some of the neediest and most difficult to educate.

While the losses have been especially steep in long-battered cities like Cleveland and Detroit, enrollment has also fallen significantly in places suffering through the recent economic downturn, like Broward County, Fla., San Bernardino, Calif., and Tucson, Ariz., according to the latest available data from the Department of Education, analyzed for The New York Times. Urban districts like Philadelphia and Columbus, Ohio, are facing an exodus even as the school-age population has increased.

Enrollment in the New York City schools, the largest district in the country, was flat from 2005 to 2010, but both Chicago and Los Angeles lost students, with declining birthrates and competition from charter schools cited as among the reasons.

Because school financing is often allocated on a per-pupil basis, plummeting enrollment can mean fewer teachers will be needed. But it can also affect the depth of a district’s curriculum, jeopardizing programs in foreign languages, music or art.

While large districts lost students in the 1970s as middle class families left big cities for the suburbs, districts are losing students now for a variety of reasons. The economy and home foreclosure crisis drove some families from one school system into another. Hundreds of children from immigrant families have left districts in Arizona and California as their parents have lost jobs. Legal crackdowns have also prompted many families to return to their home countries.

In some cases, the collapse of housing prices has led homeowners to stay put, making it difficult for new families — and new prospective students — to move in and take their place.

But some say the schools are partly to blame.

“We have record-low confidence in our public schools,” said Kevin Johnson, the mayor of Sacramento, Calif., and head of education policy for the U.S. Conference of Mayors. (He is married to Michelle Rhee, the lightning rod former chancellor of the Washington public schools and now an advocate for data-driven reform). “If we have high-quality choices in all neighborhoods, you don’t have that exodus taking place,” he said.

The rise of charter schools has accelerated some enrollment declines. The number of students fell about 5 percent in traditional public school districts between 2005 and 2010; by comparison, the number of students in all-charter districts soared by close to 60 percent, according to the Department of Education data. Thousands of students have moved into charter schools in districts with both traditional public and charter schools.

Although the total number of students in charter schools is just 5 percent of all public school children, it has had a striking effect in some cities. In Columbus, Ohio, for example, enrollment in city schools declined by more than 10 percent — or about 6,150 students — between 2005 and 2010, even as charter schools gained close to 9,000 students.

A year ago, Tanya Moton withdrew her daughter, Dy’Mon Starks, 12, from a public school and signed her up for Graham Expeditionary Middle School, a nearby charter school.

“The classes were too big, the kids were unruly and didn’t pay attention to the teachers,” Moton said of the former school.

She said she sought help for her daughter’s dyslexia at her former school, but officials “claimed that she didn’t need it.” After transferring to Graham, Moton said, “one of the teachers stayed after school every Friday to help her.”

During the recession and weak recovery, pinched state financing and dwindling property taxes forced many public schools to shed teachers and cut programs. “The fewer students we have, the fewer dollars we’re getting,” from the state and federal government, said Matthew E. Stanski, chief financial officer of Prince George’s County Public Schools in Maryland, where enrollment has fallen by almost 5 percent in five years, despite sharp gains in nearby counties.Officials have laid off about 100 teachers and district employees, cut prekindergarten to half days and canceled some athletic programs, Stanski said.

In Los Angeles, the district has dismissed more than 8,500 teachers and other education workers in the last four years as enrollment fell by about 56,000 students. The Mesa Unified District, which lost 7,155 students between 2005 and 2010, has closed four middle schools in the last three years, delayed new textbook purchases, and laid off librarians.

The students left behind in some of these large districts are increasingly children with disabilities, in poverty or learning English as a second language.

Jeff Warner, a spokesman for the Columbus City Schools, said that enrollment appears to be stabilizing, but it can be difficult to compete against suburban and charter schools because of the district’s higher proportion of students requiring special education services.

In Cleveland, where enrollment fell by nearly a fifth between 2005 and 2010, the number of students requiring special education services has risen from 17 percent of the student body to 23 percent, up from just under 14 percent a decade ago, according to the Cleveland Metropolitan School District.

Such trends alarm those who worry about the increasing inequity in schools.

“I see greater stratification and greater segregation,” said Randi Weingarten, president of the American Federation of Teachers.

Educators are concerned that a vicious cycle will set in. Some of the largest public school systems in the country are in danger of becoming “the schools that nobody wants,” said Jeffrey Mirel, an education historian at the University of Michigan.

Jeanmarie Hedges, a mother of two teenage sons, moved her family out of Prince George’s County two years ago because the proportion of students passing standardized tests was much lower than in neighboring Charles County, Md.

Hedges said she was also driven by fear of violence in the school. “Some of our friends went there and they were beaten up a lot,” she said.

A. Duane Arbogast, acting deputy superintendent for academics in Prince George’s County, said he recognized the challenge of persuading families to send their children to public schools.

“We simply have to get better and provide an education that people of all social classes would be proud of,” said Arbogast, who cited a new health sciences academy and a planned performing arts high school in his district.

But declining enrollment can force tough trade-offs.

“If you want to offer Spanish but you only have 80 kids taking Spanish, then your cost per pupil” is larger than if you have 500 in Spanish classes, said Jonathan Travers, director at Education Resource Strategies, a nonprofit consulting group that helps school systems adjust to changes in enrollment.

Before the Mesa district closed Brimhall Junior High School this year, the school lost teachers in art, music and technology in part because of a declining student head count. That made it harder for the school, which faces competition from many charter schools, to attract students.

“Education has gotten to be almost a sales job,” said Susan Chard, who taught seventh-grade math at Brimhall for 18 years. “You want to provide reasons for parents to bring their children to your school.”

© 2012 The New York Times Company