The lights went down. The screen on the auditorium stage lit up with the initials "FDM," and D.C. School Superintendent Floretta D. McKenzie -- who has announced her resignation -- began a 90-minute summation of her six years as head of the city's public school system.

Washington has become "one of the best school districts in the country," McKenzie said. "I am not saying urban any more. I am saying one of the best in the country."

She paused, but no one in the audience of about 800 D.C. school administrators responded. When McKenzie wound up her presentation, some stood to cheer her, but an equal number quickly scurried out of the Roosevelt High School auditorium to their cars.

After six years in office, the response to McKenzie's record is mixed. She wins warm praise from school board members in public, but in private some of these same people have strongly criticized her. She has gained wide support from city political leaders and business executives, though few in either group have their own children in the public schools.

Over the six years, D.C. school budgets have climbed, class size has been reduced, computers and new textbooks have proliferated. Achievement test scores in elementary schools reached national norms, though they dropped this year when the test was changed.

But in most junior and senior high schools major problems persist: low achievement, high dropout rates and recurring struggles against drugs and teen pregnancy.

Despite the gains that the system has made during McKenzie's tenure, its high school students are still in a position similar to those in many big-city school systems.

"In some of the ways we measure progress, you might not see much, but I think we've had some really dramatic changes in our senior high schools," McKenzie said in an interview a week ago. "There's a new esprit de corps. Attendance has improved. The behavior of the students has improved . . . . There's been meaningful improvement in many of the schools."

McKenzie, who has said she will leave at the end of the school term in mid-winter to become an educational consultant, has been a cautious, nonconfrontational administrator.

She has avoided the major controversies that marked the tenure of other D.C. superintendents in the last 25 years. Almost all her public encounters with the school board have gone well. Her public relations efforts, headed by Janis Cromer, who is leaving to help form the new consulting group with McKenzie, are marked by smoothly written statements, good-looking reports, and canny decisions on when McKenzie herself will speak to reporters. McKenzie usually announces the good news; Cromer usually responds when there are serious problems.

"McKenzie is a remarkable public relations person," said school board member R. Calvin Lockridge (Ward 8), who opposed her appointment and has often criticized her since. "She's kept things quiet. But there is a wide gap between what is viewed as the success of the school system and its actual performance."

"She's been extremely successful in her ability to put a good face forward for the schools," said Rod Boggs, counsel to Parents United, a lobbying group for school funds. "And that's very important for building confidence and support. You don't come upon somebody with that kind of presence every day."

Ernest L. Boyer, the president of the Carnegie Foundation for the Advancement of Teaching and McKenzie's boss when she was a deputy U.S. commissioner of education in the Carter administration, said McKenzie's programs in the District are "only a beginning and there's much left to be done. But there is a legacy there for her successor who doesn't have to build on the shambles that you have some other places."

When McKenzie became superintendent in July 1981, there already had been considerable progress under her predecessor, Vincent E. Reed, who succeeded Barbara A. Sizemore in October 1975 when the schools were at a low point in student achievement and bureaucratic disorder.

"What Vince Reed did was to strengthen the management and start building the curriculum and raising the test scores," said Julius W. Hobson Jr., a member of the board that hired Reed. Hobson now is assistant director of the city's office for intergovernmental relations. Reed is now vice president for communications of The Washington Post.

McKenzie "picked up on {Reed's} competency-based curriculum and strengthened it," Hobson said. "There's more pride in the school system and a lot more dedication . . . . I can't remember the last superintendent who was able to get as much for the school budget as she did."

One of the prime reasons for increased confidence in the schools, Hobson said, has been the scores of D.C. students on standardized achievement exams. Raising these scores has been a major goal of both Reed and McKenzie, as well as for many other superintendents across the country. The competence-based curriculum has been carefully aimed at the skills that the exams test.

However, raising the scores has been a somewhat elusive goal. The averages in both reading and mathematics rose steadily and substantially from 1979 until 1983 -- two years under Reed, two years under McKenzie, and a half-year under James T. Guines, who served as acting superintendent in 1981 and played a major role under both leaders as associate superintendent for instruction. After that, however, the only regular gains came in ninth grade.

Last spring, for the first time in 12 years, the District schools changed the standardized tests they administer, a change McKenzie had been reluctant to make because scores generally drop when a new test is introduced.

The results fell below national norms in all grades tested except for mathematics in the third and sixth grades. The elementary pupils' reading scores were just a few months below national norms, but the averages for 11th graders were 2.1 years below the norm in reading and 1.8 years below the norm in mathematics. The ninth graders were three months below the norm in mathematics and almost a year below in reading.

The test results, which normally had been featured in McKenzie's annual reports, were not mentioned in the report this year.

On the Scholastic Aptitude Test (SAT), taken by college-bound seniors, the total score on the verbal and mathematics exams rose by 22 points in D.C. schools from 1981 to 1986, compared to a 16-point rise nationwide. But at 337 in verbal and 367 in mathematics -- each out of a possible 800 points -- the D.C. public school scores ranked in the bottom 20 percent of all students tested nationwide.

In National Merit Scholarship competition, the D.C. public schools had the largest number of semifinalists in 15 years last fall, but that group of eight high school seniors was still less than one-seventh as many as the city's private schools, whose senior class enrollment is less than a third as large. The D.C. public schools had six semifinalists in the National Achievement Scholarship Program for Outstanding Negro Students, which is widely used by colleges to identify the nation's top black students. This compared to 16 attending Prince George's schools, which has about 10 percent fewer black students than the District, and 18 at private schools in the District.

One measure McKenzie often uses to show progress is the high school dropout rate, which she said has fallen from 21 percent to 15 percent since she became superintendent. However, the school system's research department, which prepares this statistic, subtracts almost 2,000 from each class's original enrollment as an estimate of students moving out of the District before calculating those rates.

The U.S. Department of Education, using a standard methodology, reported that the District's dropout rate was about 45 percent in 1981 by comparing the number of high school graduates that year with the number in ninth grade four years earlier. According to a similar calculation this year, the dropout rate fell to 42 percent for the class of 1987.

In her speech to the school administrators, McKenzie said the proportion of D.C. high school graduates pursuing postsecondary schooling has risen in six years from 40 to 60 percent, based on a survey of student plans. However, the University of the District of Columbia, which enrolls an estimated 30 to 40 percent of D.C. students going to college, admits any applicant with a high school diploma regardless of grades or test scores. Its faculty members say they have seen no improvement in the students coming from the public schools; about 90 percent are assigned to remedial classes.

Since McKenzie became superintendent, enrollment in the school system has fallen by about 8,800 students to 85,612 in prekindergarten through 12th grade last fall.

But the declines in the 1980s have been far more modest than in the 1970s, and the school system is predicting an enrollment increase this fall for the first time in 19 years. Under McKenzie, full-day classes for 4-year-olds have been established in every elementary school in the city, giving Washington by far the largest such program in the area.

City appropriations for the schools have risen substantially, climbing from $272.3 million just before McKenzie took office to an expected $412.5 million in the new school year. With federal aid, separate funds for a pay raise, and capital improvements, the budget for 1987-88 is expected to top $500 million.

The additional money has been used for reductions in average class size, from 28 students to 20 to 26, depending on subject and grade level; increases in teacher pay; new textbooks and new programs ranging from truancy prevention to computer literacy. In the last five years, the system has spent about $30 million on computer equipment and building renovations to accommodate them. In addition, McKenzie launched a "public-private partnership" with businesses to create special programs in city high schools, although so far these enroll only about 5 percent of high school students and accounted for about 3 percent of last spring's graduates.

Even with the additional funds, McKenzie has encountered criticism from school principals, whose salaries have lagged and who complain that the superintendent has limited their authority. New principals now must be reappointed every three years by the school board, instead of receiving tenure, a change that McKenzie did not initiate but supported.

Many principals also criticize McKenzie and the school board for giving the Washington Teachers Union an agency shop arrangement, under which teachers who do not belong to the union are required to pay a service fee equal to union dues.

"We have come to a point where our position has been greatly watered down," said Inez Wood, president of the D.C. Council of School Officers. "Many people are afraid to make a stand because they don't think the top administration will be behind them."

On the other hand, the teachers union, which has clashed with many superintendents, speaks warmly of McKenzie. In a statement, union President William H. Simons said her years in office have "epitomized a spirit of cooperation with the union" and praised her "illustrious career."