Fairfax County school officials hope to build seven schools and renovate 23 others in the next five years to ease crowding and upgrade aging buildings in the region's largest school district.

Details of the 2004-08 capital improvement program will be discussed at tonight's School Board meeting, and the board is scheduled to vote on the 68-page document at the end of January.

Enrollment in Fairfax is now 162,585 and is projected to top 177,477 in 2009, then drop slightly. The program includes a 24-room addition at Westfield High School in Chantilly, which opened two years ago and is already crowded; a new high school in the Lorton area of southern Fairfax and two new elementary schools, one near the county government center and the other on Coppermine Road in western Fairfax.

School officials estimate that the program would cost about $664 million, including $182 million for new construction and $354 million for renovations. Along with projects already approved for the next decade, including building additions and installing modular classrooms, the schools' capital projects total $2.6 billion.

Capital needs in Fairfax are financed solely through bonds. The last bond referendum, for $378 million, passed by a 4 to 1 ratio. School officials will spend the next few months preparing a list of projects for a bond referendum on the November 2003 ballot. But because the county issues only $130 million annually in school bonds, many projects included in a referendum don't begin until years later.

Superintendent Daniel A. Domenech and other school advocates have lobbied the state legislature unsuccessfully to allow Northern Virginians to vote on a sales tax increase to pay for school construction projects. This year, a ballot proposal to increase the sales tax solely for transportation projects was defeated.

With gloomy economic prospects in the next year, school advocates said they will abandon the fight for construction financing and spend their time lobbying against any decrease in state education funds.

"My sense is that the failure of the transportation referendum doomed any kind of an education referendum for us," Domenech said. "Besides, our concerns continue to be all of the cuts in education that we are bracing for at the state level."

He said school officials also will focus on the coming local ballot proposal. "We have to make sure that our own bond referendum continues to be a successful event," he said.

Still, Thomas M. Brady, the chief operating officer, said officials continue to look for ways to alleviate the space crunch and improve old buildings. About 70 percent of all schools are more than 25 years old.

"We're battling for operational funds so the faint hope of trying to get construction funds is off the table," he said. "Since we're not anticipating any increase, we're seeking to be creative."

This is the first year in at least five years that the district has not bought any new trailers. Instead, officials are adding modular classrooms onto schools, seeking public-private partnerships with developers and hoping to lease vacant commercial buildings to create more space.

Crowding is "a chronic problem year after year, and we just get further and further behind," said Diane Brody, the president of the Fairfax County Council of PTAs. "It is exasperating for the parents."