D.C. school superintendent Floretta D. McKenzie yesterday urged defeat of the educational tax credit proposal, saying the referendum is "a vote of confidence" on herself and public school children. She promised to mobilize city schools to help defeat the measure on the Nov. 3 ballot.

McKenzie, who was named superintendent in June, said she will use the school system to "educate our parents" about the tax credit, which she said would "hurt young people and our struggling District government."

The superintendent received loud applause from 200 persons at a luncheon meeting of the D.C. League of Women Voters, where she made her remarks. But she drew a strong retort from proponents of the initiative, who collected more than 27,000 signatures for the proposal that would allow a deduction of up to $1,200 per pupil from D.C. income taxes for expenses at either private or public schools.

Bill Keyes, chairman of the D.C. Committee for Improved Education, said it would be "improper" for McKenzie to use public funds and employes to campaign against the initiative.

Charles M. Pike Jr., campaign manager for the group, an offshoot of the National Taxpayers Union, said McKenzie's remarks show that the superintendent herself "doesn't have much confidence in public schools because she's afraid of competition.

"We're the ones that have confidence in kids and parents," Pike said, "and want to give them a chance to go to good schools rather than be trapped in the public school system."

In her speech to the League of Women Voters, McKenzie said she felt "almost like a prime minister, needing a vote of confidence . . . .

"Give public education a vote of confidence," she exhorted, "for the whole nation to see."

McKenzie sugggested that the tax credit might be appealing because "everybody needs more money," but she added, "We do not need more money at the expense of the young people of this city."

She said her office is "putting out a fact sheet" for principals and developing other "strategies for educating our parents about the tax credit . . . . We will have to put a lot of energy into defeating it as school people."

Keyes, the tax credit committee spokesman, said later in an interview that McKenzie "should not spend her time on the tax credit referendum but on figuring out a strategy to educate our children in the best possible way . . . . The main issue with Floretta McKenzie like other officials is control. They want to control the schools. We think parents should have more control."

Yesterday the League of Women Voters joined five other civic groups in forming a new organization to fight the education tax credit. The new group, called D.C. Coalition for Public Education, is separate from another anti-tax credit group, the Save Our City Coalition, headed by City Council Chairman Arrington Dixon.

League president Sue Panzer said her organization formed the new group because it wanted "to stay separate from people running for office." The new group also includes the D.C. Congress of Parents and Teachers, the D.C. Federation of Civic Associations, and the American Civil Liberties Union.

The Dixon group is dominated by members of the City Council and other D.C. political leaders, including several possible candidates for mayor next year.

During the summer the Dixon group tried to derail the initiative by raising a long series of challenges about how the tax credit petition drive was conducted. After rejecting all the group's other objections, the D.C. Elections Board ruled in early August that most of the signatures were collected by out-of-towners who were not properly registered D. C. voters, and refused to place the initiative on the ballot.

In a brief order Friday, the D.C. Court of Appeals overturned the board's decision, and ordered a November vote. The ruling by a three-judge panel could be appealed to the full nine-member court. So far neither the elections board nor the challengers has filed an appeal.

In other points in her speech yesterday, McKenzie said:

The school system "has accepted some responsibilities we can't do. We can't raise the children. We can't do everything for them, and some of our programs seem to say that we expect to do everything . . . . The major focus of the schools must be education."

She favors "a graded structure, and promotion and retention at each grade," as called for by the pupil progress plan of her predecessor, Vincent Reed. But, McKenzie added, "It is not enough to fail young people. You must have a structure to make sure they'll learn."