FLOWERY BRANCH, Ga. » Children are returning to classrooms across the nation during one of the most tumultuous periods in American education, in which many thousands of teachers and other school workers—no one yet knows how many—were laid off in dozens of states because of plummeting state and local revenue. Many were hired back, thanks in part to $100 billion in federal stimulus money.

How much the federal money has succeeded in stabilizing schools depends on the state. In those where budget deficits have been manageable, stimulus money largely replaced plunging taxpayer revenues for schools. But in Arizona, California, Georgia and a dozen other states with overwhelming deficits, the federal money has failed to prevent the most extensive school layoffs in several decades, experts said.

When Lori Smallwood welcomed her third-grade students back to school here, it was a new beginning after a searing summer in which she lost her job, agonized over bills, got rehired and, along with all school employees here, saw her salary cut.

“;I'm just glad to be teaching,”; Smallwood said. “;After the misery of losing your job, a pay cut is a piece of cake.”;

In the hard-hit states, the shuffling of teachers out of their previous classrooms and into new ones, often in new districts or at unfamiliar grade levels—or onto unemployment—continues to disrupt instruction at thousands of schools. Experts said that seniority and dysfunctional teacher evaluation systems were forcing many districts to trim strong teachers rather than the least effective.

And in some places, teacher layoffs have pushed up class sizes. In Arizona, which is suffering one of the nation's worst fiscal crises, some classrooms were jammed with nearly 50 students when schools reopened last month, and the norm for Los Angeles high schools this fall is 42.5 students per teacher.

“;I've been in public education north of three decades, and these are the most sweeping cutbacks I've seen,”; said Michael Casserly, executive director of the Council of the Great City Schools. “;But it would have been worse without the stimulus.”;

Los Angeles Unified, the nation's second-largest district, sent layoff notices to 8,850 teachers, counselors and administrators last spring. Bolstered by stimulus money, it recently rehired some 6,700 of them, leaving about 2,150 demoted to substitute teaching or out of work. Hundreds of districts across California laid off a total of more than 20,000 teachers, according to the California Teachers Association.

In Michigan, the Detroit schools' emergency financial manager closed 29 schools and laid off 1,700 employees, including 1,000 teachers. Arizona school districts laid off 7,000 teachers in the spring, but stimulus money helped them rehire several thousand. Tucson Unified, for instance, laid off 560 teachers, but rehired 400.

Florida's second-largest system, Broward County Schools, laid off 400 teachers, but aided by stimulus money, rehired more than 100. In Washington state, many districts let employees go; Seattle laid off about 50 teachers.

Lauren Stokes, who taught high school English last year in North Carolina's Charlotte-Mecklenburg district, was laid off with about 650 of her colleagues. She sought other jobs, but stimulus money sent to the state helped her district hire her and many others back. One disappointment: Her classroom this year is a portable trailer.

“;But I'm rehired, thank goodness,”; said Stokes, who is 23. “;I'm looking forward to trying new things out on this year's batch of students.”;

Catherine Vidal, a language teacher laid off in May from a high school in Moorpark, Calif., is still out of work. Fifty-nine years old, Vidal has given up her apartment and is living, for now, on a friend's boat. Teaching has become too iffy, and she will change professions, she said.

Not only school staff members are feeling the pain, of course.

“;I struggled this year getting my three boys everything they needed,”; said Mary Lou Johnson, an unemployed office worker who went back-to-school shopping last month at a Wal-Mart in Chamblee, Ga. “;Buying their backpacks, sneakers, all the stuff for their classes—it nearly cleaned me out.”;

In Ohio, students in the South-Western City district south of Columbus returned to schools with no sports, cheerleading or band, all cut after residents voted down a property tax increase. Stimulus money allowed the district to expand services for disabled students, but it could not save extracurricular programs, said Hugh Garside, the district's treasurer.

Driving the layoffs was a precipitous decline in tax revenues that left states with a cumulative budget shortfall of $165 billion for this fiscal year, according to the Center on Budget and Policy Priorities, a research institute. About half of the 160 school superintendents from 37 states surveyed by the American Association of School Administrators said that despite receiving stimulus money, they were forced to cut teachers in core subjects. Eight out of 10 said they had cut librarians, nurses, cooks and bus drivers.

Districts unable to avoid layoffs should seek to do minimum damage by retaining outstanding teachers and culling ineffective ones, said Timothy Daly, president of the New Teacher Project, a nonprofit group. But most districts are simply dismissing teachers hired most recently, because union contracts or state laws protect tenured teachers in most states and because few districts have systems to accurately evaluate teacher performance, he said.

“;Districts tend to make their problems worse by laying off good teachers and keeping bad ones,”; Daly said.

The Hall County district northeast of Atlanta, which has 35 schools, dismissed 100 of its 2,000 teachers, said William Schofield, the superintendent. John Stape, who taught high school Spanish, and his wife, Janie, who taught third grade, were among them.

Janie Stape, 50, is still out of work. John Stape, who is 65 and has a Ph.D., found a job teaching this school year, for less pay, in a rural high school southeast of Atlanta. He said that no administrator had ever observed his teaching before the day he was laid off.

“;They didn't know whether I was a good teacher or not,”; John Stape said. Schofield said the district used student achievement data and professional judgment to identify mediocre teachers for dismissal, but he acknowledged that Hall County had to cut so many teachers that strong ones were let go, too.

“;We downsized about 50 pretty good folks,”; Schofield said. The district also trimmed salaries of all district employees by 2.4 percent. Schofield said he cut his own by 3.4 percent, bringing it to $183,000 this year, and relinquished $23,000 in bonuses.

The Hall County schools received more than $18 million in stimulus money, and without it, “;those 100 layoffs could easily have gone to 150,”; he said.

Among the Hall County educators helped by the stimulus was Smallwood, who is 25. After she lost her job teaching kindergarten, she went to her mother's home to cry, then regained her composure and circulated her resume. A principal eventually hired her to teach third grade.

“;I feel like I'm starting over again,”; she said.