Fairfax County will open the school year with about $3 million less in federal education funding tied to poverty, while Montgomery County -- the school system to which it is often compared -- will get about $2.5 million more than last year, according to state and U.S. education officials.

The reason for this discrepancy, officials say, is not a dramatic shift in the demographics of the two generally affluent suburban counties. Instead, it is traced to complex formulas used by the U.S. Department of Education to determine how much money each of the nation's school systems will receive in Title I money.

Title I is a centerpiece of the No Child Left Behind Act and the federal government's largest educational program to assist disadvantaged children. Schools can use the money to improve academic programs and hire teachers; nationally, 80 to 85 percent is spent on teachers' salaries.

In Fairfax's case, the school system is getting 26 percent less this school year than last because of a small drop in the county's population of children ages 5 to 17 who are living in poverty -- one of the factors used in allocating Title I funds, said Sandy Brown, an Education Department program analyst.

Under the federal formula, at least 5 percent of the children in a jurisdiction must be living in poverty for the school system to qualify for two kinds of funding, called Education Financial Incentive Grants and Targeted Allocation.

For the 2003-04 school year, federal officials used 1999 Census Bureau data to determine that 5.06 percent of Fairfax County's 5- to 17-year-olds lived in poverty. For this school year, the officials used an updated 2000 figure of 4.93 percent.

Though perhaps 100 children were involved in that change, Brown said, Fairfax public schools no longer qualified for nearly $3 million they had received the year before because the county figure dropped below 5 percent. "That's the formula," he said.

"It's kind of outrageous," Deirdra McLaughlin, chief financial office of Fairfax County schools, said of the funding loss. She said the school system is using operating money to absorb some of the cut, but some teaching and staff positions are being eliminated.

To make matters worse, McLaughlin said, the school system is not losing -- and may be gaining -- students who participate in the federal program for free and reduced-price lunches, a measure of poverty.

Montgomery County also experienced a decrease in its poverty rate of children ages 5 to 17, from 6.24 percent to 6.08 percent. But because its percentage remained above 5 percent, there was no loss of funds. In fact, the federal government gave Montgomery a 17 percent increase.

Brian J. Porter, chief of staff to Superintendent Jerry D. Weast, said the number of children qualifying for free and reduced-price lunches is going up and the level of poverty among the county's students is worsening. "I do know that what the new formula confirms is that poverty is a real and substantial influence on social policy in Montgomery County," Porter said. "The overwhelming affluence of the greater community cannot mask the rising level of people who are suffering from impoverishment in many different forms."

Nationally, at least half of the more than 14,000 school systems are sustaining cuts in Title I allocations this school year, according to officials who monitor the $12 billion program. In the Washington region, Prince George's County was among the biggest beneficiaries, with a $4.2 million boost from the federal government over the year before.

The D.C. school system is getting a $4.4 million increase, according to Department of Education officials.

The federal department makes its allocations to school systems based on statistics involving poverty levels in counties and cities, not school systems. Education departments in each state then make adjustments to that federal allocation, withholding 1 percent for administrative costs and other uses mandated by No Child Left Behind.

Once the money reaches a school system, it is divided among schools based on the number of students qualifying for free and reduced-price lunches. However, once a school has been granted Title I money, it can use those funds for all students in the school, not just the underprivileged.

School districts are required to spend up to 20 percent of their Title I allocations on offering school choice to families -- the option of transferring to a better-performing school -- and supplemental services such as tutoring.

Jack D. Dale, the new superintendent of Fairfax schools, said it was unfair that his system had to sustain such a funding loss in one year, especially when more schools are facing expensive sanctions for failing to make academic progress under No Child Left Behind.

"It's a double-edged sword," Dale said. "You are reducing funds from the federal government for these schools, and at the same time we have the No Child Left Behind sanctions for schools that don't make adequate yearly progress. It makes you question how much value there is in the Title I program, if you take the program and have sanctions that are worse than having no [Title I] money."