New D.C. School Superintendent Floretta D. McKenzie says she will attempt to win school board approval next year to replace semester-by-semester promotion with a system that probably would call for promotions only at the end of the third, sixth and ninth grades.

The current promotions program, under which 3,800 first- through third-graders failed last year when they did not accomplish their required work, will be expanded to the fourth, fifth and sixth grades as classes start today.

McKenzie said the change from semester-by-semester promotions to promotions every third year, starting with the third grade, is necessary to give slower learning students more time to learn the required work. At the same time, she said pupils learning at their respective grade levels or doing more advanced work could still move ahead to more challenging subjects.

"Ours is one of the most ambitious programs in the country with the least amount of resources," she said. "I do believe in promotion standards, but I do not believe this system has the resources" to handle the current plan.

McKenzie's comments on the promotions plan came during an interview last week as she prepared to start her first year as the $55,400-a-year superintendent of the D.C. school system. In making her first comprehensive statement on what students, parents and teachers can expect in the next two years, McKenzie also said she will seek to:

Change the current emphasis on reading and math to include other courses in the basic education that students will receive. "We are very much for reading, writing and computation skills," McKenzie said, "but we are also very much for teaching young people about their bodies, about being good citizens and about the arts. All of it makes for an educated person."

Overhaul the city's high school curriculum to make it possible for students to take such trade courses as hotel management that would prepare them to enter the work world immediately after graduaton. But she said she also is exploring ways for college-bound students to take more courses that will assure them advanced placement in their college classes.

Develop tests to ensure that the city's 94,300 students know how to apply practically the reading, grammar and mathematics skills they learn in class to actual life situations. Those applications would include being able to read a lease, write a job application letter and figure out shopping discounts.

Start yearly performance evaluations for administrators such as the ones done now for teachers. But she stopped short of proposing that promotions and salary increases for teachers and administrators be based on how well students do in the classrooms.

McKenzie, 45, took over the city school system on July l, succeeding popular back-to-basics educator Vincent E. Reed, who is now the assistant secretary for elementary and secondary education at the U.S. Department of Education, and James T. Guines, who served as acting superintendent for six months. She took the job with a mandate from the school board to show improved student performance this year or else risk being fired.

Since then, she has been speaking before groups of parents, teachers and principals to win their support. So far, her down-to-earth personal style and the ideas she has publicly discussed have generated widespread enthusiasm.

She had not previously mentioned any intention to try to alter the semester-by-semester promotions plan, one of her first major departures from the policies she inherited from Reed.

The promotion plan the new superintendent envisions would be like Reed's in that students in every elementary grade still will be required to master certain specific skills in reading and math before they can be promoted.

But instead of having promotions in January and June, McKenzie said promotions should probably occur only at grades three, six, and nine and, of course, high school graduation after the 12th grade. Other school systems, such as those in Richmond and New York, already have limited the number of promotion "gates" for students, she said.

Last winter, Guines made the same proposal, but was sharply criticized for it by school board members who felt such a step would undermine public confidence in the already controversial promotions program, which they had approved at Reed's request.

McKenzie said she does not anticipate changing the plan during this school year. Since pupils in six grades will face the twice-a-year promotions this school year, school officials anticipate that even more students will fail.

Though she does not stress reading and math instruction as much as Reed did, McKenzie said she nonetheless plans to keep intact the Reed instructional program, called the Competency-Based Curriculum CBC . Under CBC, each course is divided into a certain number of learning objectives that students must master.

The program brought uniformity to the way each subject is taught in each school. School officials have credited CBC and its emphasis on reading and math for the slow but steady gains made by city students in grades three, six, and nine during the past three years on standardized national reading and math tests.

During the last school year, for the first time in more than a decade, third graders reached national norms in both reading and math. But the scores for grades six, nine and 11 still lag between a half year and three years behind national norms.

"While test scores are very important," McKenzie said, "we also want to know that kids can perform well by other indications, like attendance and good grades, and that they can apply to real life situations that we teach them."

While McKenzie acknowledged that the gains in the elementary grade scores were due in large part to the emphasis placed on reading and math during Reed's administration, she said, "I am suggesting that reading and math are not the only subjects to be taught . . . . There has been so much concern with reading and writing that I've discovered some schools don't have any program, say, in vocal music."

Reed, faced with the problem of students graduating from high school without being able to read, placed a large portion of the school's financial resources into teaching "the basics," reading and math. But McKenzie said she believes in the idea of "expanded basic education."

With the thrust toward reading and math, many elementary school principals gave up art and music teachers to keep their special reading and math teachers. As a result of the budget cuts that will take effect Oct. 1, many junior high schools gave up home economics, business education and industrial arts teachers to have enough teachers of English, math, history and science.

But McKenzie said she believes such teachers need not be sacrificed if they learn to incorporate lessons in reading and math into those subject areas. She said that her staff will hold training sessions to help teachers find ways of getting students to practice basic reading, writing and arithmetic regularly in various classes, no matter what the subject.

"There are all sorts of ways of applying mathematics to music," McKenzie said, citing lessons in half notes and quarter notes.

The new superintendent said she also intends to make sweeping changes in high school curricula, which are now divided between vocational schools called career development centers, and regular high schools offering a comprehensive academic program.

McKenzie said she wants to break down those divisions so that even students following a college-preparatory program can also acquire "an employable skill."

By the same token, McKenzie hopes to enlist the help of private corporations to create a series of specialized high schools, including schools for engineering, the health professions, technologies, humanities and foreign languages. Her staff includes an administrator whose sole job is to interest private corporations in making donations to the D.C. public schools.

McKenzie said she will continue Reed's plan to introduce a "life skills seminar" in the 11th grade, which all students must pass before they graduate. The District's answer to the minimum competency tests used in some school systems -- Baltimore's, for example -- the seminar would ensure that graduating students can add, subtract and multiply and read with understanding.

The seminar will be geared to real life situations such as balancing a check book or reading a travel schedule. The seminar will be required starting next year.

Whether she accomplishes her goals will depend in large part on the kind of school board that is elected Nov. 3, when five seats are being contested.

Above all, McKenzie said she wants a school board that shows "reasonableness" and will "not be seeking to find out what the superintendent is doing wrong, but support the superintendent in her efforts."

She said she believes she and the board "share the same goals for the education of the children." But she said she has had difficulty understanding why the board frequently works toward those goals "in an atmosphere of confrontation."

Reed resigned over his repeated conflicts with the board, particularly his complaint that some board members meddled in the day-to-day operations of the schools. But McKenzie so far has avoided any major scraps with the board, even though four of its ll members did not vote for her appointment as superintendent.

Like Reed, McKenzie said she is interested in attracting the middle class to the public schools, which now mostly serve families who cannot afford private education. But, she added, "I've got to give the major part of my attention to improving the program for the children already there."

She said she feels the current educational program in the public schools is "sufficient enough" now to attract middle-class families.