Proponents of the D.C educational tax credit, confronting solid resistance in some of the city's wealthier white neighborhoods, are redirecting their efforts towards middle-class blacks with children in public or private schools.

Supporters of the proposal originally expected broad support in Ward 3, the largely white, affluent section of the city west of Rock Creek Park, where many residents send their children to private schools and would be expected to benefit from passage of the measure.

But last week, early returns from proponents' telephone canvassing indicated that parts of Ward 3 oppose the measure -- in some instances by four to one.

"We're doing the worst in the city in the most affluent areas," said Charles Pike, campaign manager for the D.C. Committee for Improved Education, the sponsor of the proposal. "It's really weird. Don't ask me to explain it."

As a result, with nine days remaining until the Nov. 3 election, the committee is placing new emphasis on the city's less affluent voters, whom they say would benefit most from establishing a $1,200-per-pupil credit for parents with children in public or private schools.

To underscore that strategy, the initiative's backers will begin a $50,000 television advertising campaign Tuesday to highlight "failures" of Washington's public school system.

A 30-second commercial, filmed by an Alabama public relations firm and financed by the National Taxpayers Union, shows a series of scenes purporting to depict daily school life in Washington, including students apparently smoking marijuana.

"We talk a lot in this country about equal opportunity, but look at our D.C. school system," the announcer declares. "Schools that don't teach. . . . Drugs and violence in the classroom."

Jule Herbert of the D.C. Committee for Improved Education, the local offshoot of the National Taxpayers Union that is pushing for passage of the initiative, said the ad is designed to show "examples of children who are bored and unstimulated by a vicious public school system."

"It is aimed at people who are on the margin," Herbert added. "What we're talking about here is the mass of voters, middle-class and lower middle-class blacks, who are either struggling to send their kids to private schools or would very much like to get their kids out of the public schools."

William H. Simons, president of the Washington Teachers Union and a leader of the fight against the measure, known as Initiative No. 7, said he resented this approach.

"We don't say that there aren't problems with drugs and violence in the schools," Simons said, when told of the ads. "But instead of trying to use their influence to get funds for the public schools, they are just trying to tear them down."

Under the initiative, taxpayers would be able to reduce their D.C. income taxes by up to $1,200 per pupil for expenses they incur at either private or public schools. It also would permit nonparents and corporations to receive tax credits by contributing toward educating low-income youngsters.

Although more than 27,000 persons signed petitions to place the measure on the ballot, it has drawn considerable opposition from many sectors. The mayor, City Council and School Board are against it, as are numerous civic organizations.

The Most Rev. James A. Hickey, the Roman Catholic Archbishop of Washington, took no stand on the issue, and asked parents to decide for themselves whether to vote for the proposal.

Officials of most of the city's private schools have expressed opposition to the measure, saying it offers no tangible benefits to their institutions and would destroy the city's public schools.

It was unclear yesterday where the scenes in the television ad that purported to portray life in the city's schools were filmed.

Herbert said that William Moody, a Tuscaloosa-based media consultant he met last year while working on the presidential campaign of Libertarian Party candidate Ed Clark, came to the District over the summer and filmed the commercial. Herbert acknowledged, however, that the scenes were not filmed at a D.C. public school.

"It's none of your damn business where it was filmed," Herbert said. "This is not '60 Minutes' we're talking about."

Meanwhile, opponents of the initiative have launched their own radio advertising campaign, with a variety of 30-second commercials.

One commercial, running on stations such as WRC and WTOP, whose listeners are predominantly white, stresses the argument that passage of the initiative will drain this city of $75 million, requiring D.C. income taxes to rise by 29 percent and property taxes by 36 percent.

Another ad, placed on such predominantly black-oriented stations as WOL and WOOK-FM, uses a different approach.

"Hey, brother," the announcer says, "they're running a game on you with your taxes. You put your dollar in here, and you find over there, in some rich dude's pocket."

"It's a mean game, man, 'cause it's gambling with our kids' future," the ad concludes. "Hey, go vote 'No' on Initiative No. 7. Let 'em know they can't run a game on you."

Pike, campaign manager for the initiatitve's supporters, said that his group encountered 4-to-1 opposition when it canvassed more than 150 voters with children at the prestigious Sidwell Friends School on Wisconsin Ave. NW, where tuition for the upper grades is $4,250 a year.

The measure's backers suggest several reasons for the apparent lack of support among wealthy white parents, including the claim that many are "out of touch" with the reality of conditions in the public schools. Others attribute it to politics.

"You have to remember that Ward 3 has your upper middle-class white liberals, who think this is the worst thing they've ever heard of," says Herbert. "These are people who are perfectly content with the way things are."

Still, backers were heartened by what they claimed was 2-to-1 support among the less wealthy parents of children attending Catholic schools, where tuition is barely a fourth of what it is at the other private schools.

"They're the ones who are really going to be helped by this," said Pike. "It wasn't designed to help the parents at Sidwell Friends."