Fairfax County school officials, concerned about the stagnant test scores of black and Hispanic students, have hired a former District of Columbia school superintendent as a consultant to examine their minority achievement program.

The independent analysis, to be done by former D.C. schools chief Floretta D. McKenzie, will be the first to look at the merits and failings of the county's six-year-old effort to raise the achievement of minority students, who now represent one of every four students in Fairfax classrooms.

The move reflects growing national concern among suburban school districts, which are increasingly turning to outsiders for help.

"We know what the problems are and even where in some instances," said School Board Chairman Kohann H. Whitney (Centreville). "What we need are answers."

After a bidding process, Superintendent Robert R. Spillane recommended hiring McKenzie for $119,000 -- $37,000 more than originally budgeted for the six-month study.

One School Board member raised questions because McKenzie and Spillane were professional colleagues. However, the board was satisfied there was no conflict and unanimously approved the contract.

The situation in Fairfax mirrors that across the river in Montgomery County, which received a preliminary report last month from its own consultant lambasting its minority achievement program.

With the arrival of many non-English-speaking immigrants in the last 15 years, both Fairfax and Montgomery, affluent suburbs that once were nearly all-white, have become far more diverse. In both counties, as in schools across the nation, blacks and Hispanics on average score 20 or more percentile points lower than whites on standardized tests.

"More and more boards and superintendents are taking a high-risk position of bringing in a third party to look . . . at what can be done to improve student achievement," said McKenzie, who founded her own firm, the McKenzie Group, after resigning from her position in the District in 1988.

Minority enrollment in Fairfax has jumped dramatically in recent years, particularly in the eastern sections of the county, which have become magnets for newly arrived Hispanic and Asian immigrants.

Where once their presence was almost negligible, minorities today account for about 26.5 percent of the county's 130,000 students -- 11 percent Asian, 9.6 percent black and 5.7 percent Hispanic -- and that figure is expected to grow to 37 percent by 1998.

English-as-a-second-language classes are packed, and minorities accounted for about half of this year's enrollment growth of 2,000 students.

In the last year, increasingly frustrated community leaders have stepped up pressure on school officials to close the persistent gap in test scores.

Last fall, the NAACP called the schools' minority achievement program a "total failure," and School Board member Robert E. Frye (At Large) said Spillane should resign if he did not improve the scores.

The frustration has been particularly acute because Fairfax is among the wealthiest counties in the nation with what many consider some of the best schools in the United States.

"We're not as successful {when it comes to minority achievement}, and we find it very difficult to deal with," said School Board member Armando M. Rodriguez (Mount Vernon).

When Frye raised the idea of hiring a consultant last spring, Spillane initially balked, saying the county could conduct its own study.

Frye argued that an outsider would be more objective, and his colleagues eventually agreed.

McKenzie dismissed questions about the wisdom of hiring an educator who presided over a school district plagued by low achievement among its students, most of whom are black.

"Most people only see me as having been in D.C.," she said. "But they don't remember I spent a large part of my career in Montgomery County as area superintendent and deputy superintendent."

McKenzie, who is a longtime friend of Fairfax Deputy Superintendent Loretta C. Webb, her liaison for the study, also noted that her firm has conducted studies of the Pittsburgh, Dallas and Anne Arundel County school systems.

NAACP President L. Marie Guillory said she was less concerned with how the school district raises achievement, so long as there are results.

"It's a good idea to bring in an objective third party to look at the programs," she said.

"I hope it's not a scapegoat situation that's being set up to avoid focusing on minority achievement," she said. "I don't think you need to hire a consultant to decide you need to focus on minority achievement."