The D.C. Board of Education yesterday unanimously approved a one-year, 16-school test of a plan to discontinue its unique and controversial practice of midyear promotions and failures for elementary school students.

In approving the study recommended by Superintendent Floretta D. McKenzie, the board effectively postponed action on McKenzie's earlier recommendation that the midyear promotion policy be scrapped altogether at the city's 125 elementary schools.

McKenzie said yesterday that she has pushed for dropping the midyear plan because she thinks the prospect of twice-yearly failures for slow students is psychologically discouraging, and because the system burdens teachers with added paperwork and bureaucracy.

The board's current student progress plan, adopted during the 1980-81 school year, gives elementary students passing or failing grades at midyear and holds back those who have not mastered essential reading and math skills.

McKenzie and board member Linda W. Cropp (Ward 4), who chairs the board's educational programs committee, stressed that the school system is not relaxing its standards nor slackening its effort to quickly identify failing students, to discuss the prospective failure with parents and to provide special attention.

McKenzie recommended scrapping the system even though D.C. schools have seen steady improvement in the percentage of students promoted. Only 72.7 percent were promoted in January 1982, but the percentage climbed to 91.5 percent in June 1983.

"We think the current system works," McKenzie said in an interview before the board's vote. "But we think it can work as well or better without twice-a-year declarations of failure or success."

Under the plan approved yesterday, students at the 16 schools will receive midyear report cards indicating whether they are performing at, above or below their grade level. But they will not be given a pass-fail designation at midyear. The schools have not yet been selected.

Washington has the only school system in the country with midyear promotions, according to school officials, who told the board that both the National Institute of Education and the University of the District of Columbia have recommended a return to annual promotions.

Youngsters who suffer the stigma of midyear failure are often so discouraged they do worse in the second semester, McKenzie said. Referring to her proposed change, she said, "If it can help one kid not to become frustrated and defeated, it will be worth it."

Several board members have been cautious about McKenzie's recommendation, fearful that the board will be tampering with success and will appear to be retreating from its recently adopted tougher standards. Board member Eugene Kinlow, former board president, said, "We have devoted so much time and energy and psychic dollars to the (existing) system, we must carefully investigate before we change."

School officials have said the midyear promotion plan is not necessarily the main reason for the recent improvement in achievement levels. A key factor, they say, is the competency-based curriculum adopted at the same time.

The midyear system is burdensome, McKenzie said, particularly because students may pass reading at midyear, but fail math, or vice versa, requiring teachers to maintain numerous categories in record-keeping.

McKenzie is to report to the board by Sept. 30 on how and where the study will be conducted. She said the best gauge of the new plan's success will probably be whether the number of end-of-year promotions increases and whether particular students with failures improve.