Harper Park Middle School opened in Leesburg just four months ago, but it is already so crowded that school officials said last week that they will move next year's eighth-grade class to Stone Bridge High School.

The estimated total of 465 eighth-grade students will attend classes in a separate part of the new high school, which is under construction nearby in Ashburn and is expected to be under-capacity when it opens in August because it will not have a senior class its first year.

A Harper Park assistant principal, a guidance counselor and an undetermined number of Harper Park teachers will be at Stone Bridge with the eighth-graders at all times. School officials said they expect the middle school students to interact rarely with ninth-, 10th- and 11th-graders.

"Our intent here is not to add an eighth grade to the high school," School Superintendent Edgar B. Hatrick III told the School Board. "We'd be using their space, that's all."

The move will be only temporary. In August 2001, Eagle Ridge Middle School is scheduled to open in Ashburn and will ease crowding at Harper Park, officials said. The eighth-graders who attended classes at Stone Bridge will stay at the campus for high school.

The School Board, which does not have to approve the plan, first learned about it Tuesday and made no public comments.

Harper Park was built for 1,184 students, but as of Dec. 30, 1,223 were enrolled. Next year, about 1,590 sixth-, seventh- and eighth-graders are expected to enroll.

Sam Adamo, the district's director of planning and legislative services, said school officials had expected more than 1,184 students to enroll next year, in part to relieve cramped quarters at 24-year-old Simpson Middle School in Leesburg. But the new projections have exceeded the district's estimates.

Principals at Stone Bridge and Harper Park have met with parents and administrators for several weeks to find ways to reduce crowding at the middle school, said Sharon D. Ackerman, assistant superintendent for instruction. Francis R. Fera, the principal at Harper Park, could not be reached for comment, but Ackerman said he plans to speak at several PTA meetings about the transfer.

"We're convinced that this really is a viable solution," she said.

In past years, officials have moved fourth- and fifth-graders to middle schools and have sent sixth-graders to elementary schools to relieve cramped buildings, she said.

Administrators considered adding 10 trailers to the Harper Park campus but rejected the idea for a variety of reasons, including cost and safety. The building's core facilities--cafeteria, media center, gymnasium--were not built to accommodate nearly 1,600 students, Ackerman said.