Seven years ago, parents in the upper-middle-income community of Chevy Chase received an open letter about Rosemary Hills Elementary School in Silver Spring where their children would enroll as part of Montgomery County's first major effort to integrate schools by busing.

The letter, from the county school superintendent, spoke only in positive tones about the academic program and made no mention of the divisions that already had split Chevy Chase.

Last week, Chevy Chase residents again received a letter about Rosemary Hills. In this one, however, the optimistic tone was dropped. In its stead is an extraordinarily candid appeal from Superintendent Edward Andrews to parents, asking them to consider enrolling their children at Rosemary Hills before sending them to private schools.

The two letters and the distance between them reflect the scars of one of Montgomery County's toughest battles: persuading white and upper-middle-income parents that a good educational program can exist--and has existed--when children of a wide range of racial, cultural and economic backgrounds are bused out of their neighborhoods to go to school together.

Beginning in September 1976, the buses rolled between Chevy Chase Elementary and Rosemary Hills. The two schools were separated by only four miles, but the economic and cultural distance was much greater.

Chevy Chase, for the most part, is home to lawyers and other highly educated professionals, most of them white. Houses are large and lawns spacious. Rosemary Hills is populated by blue-collar workers, mostly blacks and Hispanics, who live in brick high-rises or small brick homes.

For six years, the two groups of children attended Rosemary Hills for kindergarten through second grade and Chevy Chase for grades three through six. It was to be the kind of noble experiment Montgomery County residents pointed to when boasting of their liberal reputation. But last year, a conservative-dominated school board brought the experiment to an end, agreeing with some Chevy Chase parents that it had failed. Both schools reverted to separate programs of kindergarten through sixth grade.

Next fall, busing will resume between Chevy Chase and Rosemary Hills, the result of a vote to reinstate it by a school board elected last fall.

School and county officials realize they have reached a critical point. For the first time in the county's history, the majority of white parents from one area--Chevy Chase Elementary--whose children are assigned next year to a school in a predominantly minority area--Rosemary Hills--have signed sworn affidavits that they will not permit their children to attend the minority-area school.

Their children, they say, are one investment they don't want to take chances with. Race has nothing to do with it, they add, but when economic circumstances and achievement levels are so vastly different, one school cannot provide the resources necessary to ensure their children will succeed.

"I can't in good conscience send my daughter to a school where I don't think she will get the attention she needs," says one of the parents who signed an affidavit but refused to be quoted by name. "Of course, there will be gifted black children at Rosemary Hills, but the truth of the matter is that there are more low-achievers that come from lower-income backgrounds than there are from high-income backgrounds."

It's important to win those parents over, says board president Blair Ewing, who believes the success of his tenure will partly be measured by the outcome of desegregation efforts.

"We have reached the point where we must decide whether we are going to have a single unified school system and one not divided by race and class and other types of differences," he says. "No one in the school system has any illusions that it will be easy . . . . If integration is to succeed anywhere, it should be in Montgomery County. We have the general support of the county government, we have the wealth and talent . . . . we now need the will of the parents to do it."

More is riding on a successful desegregation effort than the survival of Rosemary Hills Elementary, say Ewing and other school and county officials. If Chevy Chase parents cannot be encouraged to participate, these officials wonder if more and more of the county's white parents will do what they have done in neighboring Prince George's County and some suburban systems and remove their children from public schools.

To convince parents to stick with public schools such as Rosemary Hills, school officials would rather concentrate on future plans for the three Chevy Chase-area elementary schools than talk about the past. In September, children from North Chevy Chase and Chevy Chase elementaries will be bused to Rosemary Hills for kindergarten through second grade and then will enroll at one of the other two Chevy Chase schools for the remaining four grades. Rosemary Hills, which without an integration plan would be more than 90-percent minority, is projected to have a minority enrollment of 49 percent.

But most school officials also realize that before the future of Rosemary Hills can be discussed, the past must be clarified. "Be fully informed," Andrews writes in his letter.

School officials and teachers involved in the Rosemary Hills desegregation effort adamantly defend the quality of the academic program and say high achievers as well as remedial pupils performed well.

"Like any school, the school has had its problems and there were changes we might have made," said Andrews in an interview recently. "But it was a very good school that was well on its way to becoming an excellent school. My regret is that there have been so many disruptions."

During the six years of the exchange program, says area superintendent Alan Dodd, pupils enjoyed one of the smallest teacher/pupil ratios of any county elementary school. Additionally, most classrooms had teacher aides--in a normal county school there is only one aide--and a specialist was hired to devise curricula for individual pupils' needs, a position nonexistent in most schools.

Some Chevy Chase parents, however, argue that the resources were not enough to meet the needs of a school whose pupil population was split so radically along economic and achievement lines. And, after an initially strong start the school system's interest in the program dwindled and Rosemary Hills became just another school, charge some parents.

"When you have gigantic diversity between two groups of children in one classroom, teachers and aides are naturally going to help pupils who need the most," said Chevy Chase PTA president Kathy Wolf in an interview earlier this year. Wolf had two children who attended Rosemary Hills and considers herself a liberal. "My children did well at Rosemary Hills, but it is only logical that there is going to be some tipping point where having too wide a gap among too many children along socio-economic lines is going to hurt some students."

School officials reject Wolf's arguments, pointing out that they overcame the differences in performance by grouping pupils by ability. Officials also point to test scores that they say are in their favor. Although projections about how these pupils may have fared in a different school setting cannot be made, school officials say it is obvious that high achievers were not hurt by their Rosemary Hills experience.

"Throughout the county you will hear parents say you are not challenging their high-achieving children. We heard it at Rosemary Hills," says former Rosemary Hills principal Gerald Johnson, now principal at Maryvale Elementary in Rockville. "But I always said come up and give me the data and we'll do something about it. No one ever could."

School officials, citing pupil privacy, would not release individual test results that would indicate over a period of years how pupils from the Rosemary Hills and Chevy Chase areas performed after spending their primary years at Rosemary Hills.

But test data compiled in 1981 for a one-year-period, while the previous school board, whose majority was against busing, was considering closing the school, indicate that high achievers performed well at the school.

Twenty percent of the pupils in third grade at Chevy Chase, who had spent at least two years at Rosemary Hills, scored in the top one percentile nationally in tests taken only months after leaving Rosemary Hills. The average black pupil and white pupil at the school scored close to county-wide averages. And while only nine percent of the first-grade pupils at Rosemary Hills in 1980 were reading at grade level when they first enrolled, 83 percent had reached that level by spring of that academic year.

These statistics back up recent research on national desegregation programs that indicate, contrary to earlier studies, white pupils are not affected academically by busing and that black pupils usually score a few points higher than they would if enrolled in overwhelmingly black schools.

In Berkeley, Calif., where the school board undertook a large-scale busing program and children of widely stratified economic levels were bused to school together, recent test scores show both blacks and whites improving.

"Almost as a law, you can say that there are no studies that show white students are adversely affected by desegregation ," says Meyer Weinberg, a national expert on desegregation from the University of Massachusetts at Amherst.

The woman who signed an affidavit saying she would not enroll her child in kindergarten at Rosemary Hills says she believes in public schools and wants her child to learn in a diversified setting.

She signed the statement, she says, because she heard "all these horrible rumors" about Rosemary Hills. Today, however, like some other Chevy Chase parents, she is reconsidering her decision. She says she still feels the old program at Rosemary Hills was not a good one, but that recent overtures from school officials and county officials may cause her to change her mind.

The county council recently approved an extra $200,000 to create an accelerated math and science program and to hire more teacher aides for the three schools involved in the desegregation effort. But if not enough Chevy Chase parents sign up their children next week during the kindergarten-roundup at Rosemary Hills, the woman says, she may stick to her decision not to send her daughter there.

Other parents feel differently.

"I think it will be the best deal in town," says Chevy Chase resident Janice Yaden, who has one child at Chevy Chase and one she will enroll next year in kindergarten at Rosemary Hills. "The school board did not treat the Chevy Chase community well. But it's my perception that the school system knows that its reputation is on the line to make this program work, and they know that they have to have good programs, good teachers and a good principal.

"I'm willing to give it a chance. I've never visited the school, but why should I? I never visited Chevy Chase before my son enrolled there."

Dodd, who as area superintendent supervised the birth of the earlier desegregation program, has decided to postpone retirement a year so that Yaden and other parents will be pleased with Rosemary Hills' new academic program. As for the past, he says, "I don't know if we will ever be able to convince some people that what was at Rosemary Hills was good.

"It's a little like my wife trying to persuade me about something that I may never change my mind about. But from my point of view, I truly believe that Rosemary Hills was a success for all children. If we only had all the resources we had at Rosemary Hills at other schools, we'd have terrific programs everywhere."