A lawyer for the Montgomery County school board told the Maryland Board of Education here today that the possible flight of a large number of white students from high-minority-enrollment Rosemary Hills Elementary School in Silver Spring is insufficient reason to reject an integration plan for that school.

E. Stephen Derby, testifying at a hearing at which some residents of the predominantly white Chevy Chase community sought to overturn the plan, urged the state board to reject the appeal.

It includes sworn statements by 31 of 42 families there that they will enroll their kindergarten-age childen in private school next fall rather than send them to Rosemary Hills if the plan is put into effect.

Lawyers for the Chevy Chase community argued that the integration plan set to be reinstated in September is "critically defective' and that to ignore the sworn statements from the parents about how many would not send their children to Rosemary Hills was a failure to abide by the local board's guidelines on racial enrollment.

Under its guidelines, the Montgomery board is required to begin action to desegregate schools when the minority enrollment exceeds 64 percent. Chevy Chase parents have argued, backed by school estimates, that without their participation the minority population at Rosemary Hills would be at least 60 percent.

"It's a sociological fact that some of these parents will not attend that school and that some who do attend will withdraw," William Moore told the board. To ignore these facts, added Moore, "is an intent to evade the impact of very important evidence."

Moore argued that Chevy Chase parents have made a sincere effort for five years to make the integration program work, but that it failed on both integration and educational grounds. Chevy Chase parents have said the wide differences in economic and cultural backgrounds between the two groups of students cause too many educational difficulties that cannot be met in one classroom.

In addition, Moore argued that under the current plan both Chevy Chase and Rosemary Hills are well-integrated schools. Chevy Chase's student population is 36.8 percent minority, compared with about 50 percent minority enrollment at Rosemary Hills.

Without an integration plan, school planners say the minority enrollment at Rosemary Hills next fall would exceed 90 percent.

Under the plan reinstated by the county board last month, students from Chevy Chase and North Chevy Chase elementary schools will be bused to Rosemary Hills for preschool through second grade. Students from the three schools will then be split between North Chevy Chase and Chevy Chase for grades three through six.

"We do not question the right of middle class parents who can afford to send their children to private school . . . ," Derby told the nine-member state board. "But because people are threatening to leave public schools, does (the county board) have to change what is otherwise a good educational decision? . . . It is not the kind of thing the county board should be responding to."

Derby also said the Chevy Chase community should be willing to give the new educational programs at Rosemary Hills a chance.

Last week, the board voted to ask the county for an additional $206,000 for the programs at Chevy Chase, Rosemary Hills and North Chevy Chevy Chase. The money, which will mean about $70,000 more per school than the average county elementary school, will be used to hire 14 more teacher aides, institute special accelerated programs for gifted students and to begin a math and computer magnet program.

State board president Joanne T. Goldsmith said the board will decide the appeal on April 27.