The Fairfax County public school system is scrambling to find jobs to absorb its largest teacher surplus in recent years, school officials said.

While other metropolitan area school systems laid off a number of teachers last spring, Fairfax decided to hold down layoffs and gamble on being able to place most of its extra teachers. Now, Fairfax has discovered it lost the gamble.

At the end of the first day of school Monday, the system still had not placed 75 teachers.

"The school system made a big mistake in overestimating last year on the number of teachers they needed," said Marilyn Rogers, president of the Fairfax Education Association, the county's largest teacher organization. "Because of the economy, teachers aren't leaving the profession and new families aren't moving in like they used to."

School officials said the weak economy skewed the system's usual formula for estimating available jobs.

"Our past experiences aren't helping us this year or we wouldn't find ourselves in this dilemma," said R. Warren Eisenhower, assistant superintendent for personnel services.

The surplus teachers, all of whom have contracts for the current school year, will be placed throughout the school system as special resource teachers, substitutes and remedial teachers until permanent positions can be found, Eisenhower said.

The school system began the summer with more than 130 surplus teachers but found openings for about 55 in the last few weeks because of last-minute student enrollments and a few unexpected teacher resignations, officials said.

Eisenhower said the school system usually begins the summer with about 50 extra teachers on the payroll. In past years, the schools have been able to count on a 6 to 7 percent teacher turnover rate that created positions for any teachers still without jobs when school opened. This year, however, the number of resignations has fallen far short of projections.

School officials blame the unusually low turnover on the economy, with more teachers hestitating to give up secure positions in the face of uncertain financial conditions.

In some cases, Eisenhower said, teachers decided to keep their Fairfax jobs, although their spouses took jobs in other areas. Most of those teachers remained behind because their families need both incomes and they have been unable to sell their houses, he said.

The depressed economy also has affected enrollment. Fewer families with school-aged children are moving into the growth areas of the county, Eisenhower said. As a result, he said, many teacher surpluses have occurred at elementary schools where student enrollments are substantially below original estimates.

School officials estimated an enrollment of about 122,000 for this school year, down about 2,000 from last year. Officials now predict enrollments may be even lower. An official count for the new school year won't be taken for several days.

Except for Prince William County, all Northern Virginia school districts laid off teachers last spring to avoid surpluses this fall. Arlington laid off 119 teachers; Alexandria, 27; and Loudoun, 36. Many have since been rehired to fill unexpected openings.

Fairfax County sent layoff notices to 28 teachers, an unusually small number for a district that has the largest enrollment and faculty in Northern Virginia. Since then, all but four of the teachers have been rehired. Most were rehired because they had special skills needed for specific jobs.

"Other school systems went ahead with wholesale rifs," Rogers said. "To their credit, Fairfax always tried to be conservative. They tried to be humane because of economic conditions, and it backfired on them."

She said this year's problems could spell trouble for teachers next year if the school system decides to take a tougher stand and lay off more teachers.

For this year, the surplus will mean placing many teachers in jobs normally filled by lower-paid aides or substitutes. It also will mean fewer jobs for part-time substitutes.

"Teachers are glad to have jobs," Rogers said. "But they don't like the situation they're being thrown into."

Although the teacher surplus is a headache for school administrators, it will be an advantage for students, Rogers said. Teacher-student ratios will be lower in some schools, and there will be more help for slower students and more qualified substitute teachers.

"The bad side will be the reshuffling of children as the year progresses, with students possibly being in several different classes before all the teachers are placed," Rogers said.