Public school enrollment will climb to 47,632 students by the 2005-2006 school year in fast-growing Loudoun County, according to projections released this week, although the rate of growth is expected to begin slowing over the next few years.

This year, 28,787 students attend classes on 45 campuses; an estimated 9 percent more students will enroll next year, according to figures made public Tuesday. Loudoun's average increase in recent years has been about 2,000 students annually.

But the growth rate is expected to decline to 8 percent in the 2005-2006 school year, said Sam Adamo, the school system's director of planning and legislative services.

Even so, Adamo said, the district must continue building new schools. Officials have said that 26 new campuses, including three now underway, will be needed over the next six years to accommodate the influx of students in Loudoun, the nation's third-fastest growing school district and the fastest in Virginia.

"We'll still be facing some fairly significant challenges about growth in the future," he said.

Three new schools will open in August: Stone Bridge High in Ashburn, Little River Elementary in South Riding and Mill Run Elementary in Broadlands. Expansions to ease crowding are underway at three other elementary schools.

School Board Chairman Joseph W. Vogric (Dulles) said he hoped the new enrollment statistics would dispel thoughts that the district doesn't need more campuses.

"The percentage is going down, but the number of students is still increasing," he said.

On Nov. 2, Loudoun will vote on a $100 million bond referendum to finance construction of four more schools: an elementary school in Lansdowne, a middle school in Countryside, an intermediate school in western Loudoun and a high school in Leesburg. The referendum includes a proposal to expand Lucketts Elementary School, among other projects.

Adamo said he considers four factors in estimating future enrollment: county birth rates, building permits issued in Loudoun, the state-mandated school census, and data about the number of families moving into the county.

How accurate is that method? This year's student projection was off by only 97 students, he said.

One reason for the school district's continued growth is a county birth rate that keeps rising--by 38 percent during the last five years alone. Statewide, the birth rate dropped 5.5 percent during the same period.

Birth rates nationwide peaked in 1992, Adamo said, but "Loudoun has continued on quite an upward spiral."

Most of the student population boom, though, is the result of families moving into the county, Adamo said, many of them drawn by the influx of technology companies in Northern Virginia.

An estimated 5,353 building permits were issued in Loudoun last year, a 47 percent increase over 1997. And there is no end in sight. Nearly 4,000 permits were issued in the first eight months of 1999, about half of them in the Broad Run section of eastern Loudoun.

"We are marching in lock step with the economy and the employment sector in Loudoun County," Adamo said.