More than a third of all Fairfax County elementary schools will undergo boundary changes next year, in an attempt to redistribute the dwindling population of school-aged children.

In all, 45 schools will open in September with new boundaries, and school administrators admit that is a record number of changes, even in a county where boundary changes are an annual ritual.

"Last year we changed something like 10 or 12 boundaries," said Ralph Bell of the school system's planning services office. Bell and others in the boundary department are still mapping out the extensive changes that will affect schools throughout the county.

School officials say all families affected by the changes will be notified early this summer.

In addition to the declining enrollment, two other factors contributed to changes for next year -- the closing of seven schools, approved by the school board late last month, and the opening of two elementary schools next fall, Terra Centre and Forestville.

The boundary adjustments, as the school officials call them, were approved two weeks ago. In the same meeting, the school board also authorized the closing of the seven elementary schools. While the changes were overshadowed by the closings, a number of parents said they were just as angry about having their children transferred as were the parents whose children's schools were closed. A recurrent argument during the one night of hearings on the boundary changes was that a boundary change is the same as a school closing to the child who must change schools.

For the firt time in recent years, observers said, not only was there an unprecedented number of changes, but of the changes recommended by the superintendent, more of them than ever before were rejected by the school board.

Bell said nearly 95 percent of the superintendent's proposals were accepted in recent years, but this time, numerous changes were made by the school board. By the end of the board meeting, 18 amendments to Superintendent L. Linton Deck's recommendation were accepted by the board.

These changes included allowing the children of Hillwood Triangle, a predominately black neighborhood near Falls Church, to continue attending Beech Tree School rather than transferring to Timber Lane, as Deck suggested.

This particular proposal drew much attention as residents of the area called Beech Tree "a model for successful integration." Beech Tree currently has a minority enrollment of about 16 percent, which would have been almost eliminated if the children from the triangle area were sent to Timber Lane. In addition, parents said the high minority enrollment at Timber Lane, currently 54 percent, would be pushed even higher. Residents of Hillwood Triangle pleaded with the board to allow their children to stay at Beech Tree, and were granted their request.

Other parents who thought they made arguments just as convincing were not as successful. Families from the Lake Forrest area of Springfield were bitterly disappointed when the school board voted to move their children from Hunt Valley Elementary School to Orange Hunt.

Parents from Lake Forest said their major concern was that the new school have "open" classrooms, and Hunt Valley is a conventional school. The change in educational philosophy and structure would be detrimental to some children, parents insisted.

While many parents, such as those in Springfield, say they are frustrated with the constant boundary changes -- and the resulting uncertainty that accompanies attending school in Fairfax County -- most say they will try to make the best of it.

Lake Forest parent Louis Consagra said last week that while he thought his children has flourished in a conventional-type school, he had told them "that no matter where they go next year, they have to do the best they can."