Parishioner Fred Plummer had just finished leading Northwest Washington's St. Gabriel Church in the final hymn and now, beneath the church's tall stained-glass windows and high, arched ceiling, he was telling some friends why he will vote for the proposed educational tax credit Nov. 3.

"I was listening to radio station WOL the other day, and this kid from Cardozo High School was saying how the educational tax credit was going to do terrible things to the public schools. And I thought to myself, we Catholics have been paying taxes for public education for 49 million years . . . but just because we decide to talk about God in school, we can't get any government funding," said an angry Plummer, a bank teller.

Across town, Fleming Brown, a retired U.S. postal worker, was standing on the stone steps of another predominantly black, middle-class parish -- St. Benedict the Moor Church near RFK Stadium --strongly criticizing the proposed $1,200 yearly tax credit.

"I am a Catholic and I believe in private school. But I also believe in public schools," said Brown, whose children attended D.C. public schools. "If you want to send your kids to private school, fine. But don't ask me to pay for it."

The views of Plummer and Brown reflect the deep divisions over the tax credit that exist among the city's middle-class, black Catholics. The 70,000 black Roman Catholics in the city have been targeted by the bill's chief supporter, the D.C. Committee for Improved Education, as crucial to any effort to get the measure passed. The committee is concerned by the apparent lack of support for the initiative in the city's wealthier, largely white areas.

The initiative, originally conceived by the National Taxpayers Union, would allow individuals to claim a credit of up to $1,200 per pupil on D.C. income taxes for educational expenses for their children in either public or private schools. A taxpayer must earn more than $20,000 a year to qualify for the full $1,200 credit.

The city's middle-class, black Catholics form a large -- and as yet untapped --voting resource for the tax credit's promoters, especially since the Roman Catholic Archbishop of Washington, the Most Rev. James A. Hickey, has directed all parish priests not to promote or even discuss the issue in church.

At the same time, Catholic school principals say they have been ordered not to give any information about the measure to students to take home to parents.

Officially, Hickey has said he is taking a neutral stand on the initiative, insisting that Catholic parents should make up their own minds on the issue.

The Rev. Raymond Kemp, an assistant to Hickey and a former D.C. school board member, said that both he and the archbishop were concerned that the petition drive to get the measure on the ballot was initiated by a group of outsiders, not D.C. residents.

The archdiocese "did not initiate the thing, we were not consulted in it," said Kemp, who predicted that it would be defeated. Hickey has "taken a lot of heat on this thing from people who wanted to see him behind it," Kemp said.

Some priests say privately that Hickey did not want to put the Catholic Church here in the position of supporting a measure that has sparked such widespread opposition from community groups and leaders. Included in the opposition are Mayor Marion Barry, School Superintendent Floretta D. McKenzie, the D.C. City Council, the Washington Teachers Union, the Urban League, and the Greater Washington Board of Trade.

Nonetheless, Hickey, as well as the U.S. Catholic Conference, the church's lobbying arm, do support the $250 proposed federal tuition tax credit for private and parochial school parents, Kemp said.

Prior to Hickey's directive, some of the predominantly white, middle-class parishes, including Annunciation, Our Lady of Victories and St. Ann's in upper Northwest, and Holy Trinity in Georgetown, had moved quickly to circulate information on the initiative among parishioners.

The initiative was mentioned at least three times in St. Ann's weekly church and school bulletins, according to one parishioner. At Annunciation, the pastor, Monsignor James Montgomery, had an open letter on the measure read at all Masses a few Sundays ago.

But at Holy Trinity, one of the wealthiest and most liberal parishes in the city, some parishioners complained when an item was included in the Sunday bulletin suggesting that such a credit might be to the parishioners' advantage, according to one of the parish priests who asked not to be named. That ended any sort of parish promotion of the initiative, he said.

While the official policy of the archdiocese is neutrality, churchgoers interviewed yesterday appeared frequently confused as to what the initiative really would do.

"I don't have a full understanding of it," said Ethelrene Parker, a St. Benedict's parishioner and part-time cafeteria aide who has put six children through parochial schools. She currently pays $2,300 a year to send her daughter Kimberly, 14, to Georgetown Visitation School.

Parker initially called the tax proposal "nonsense" because she thought -- incorrectly -- that she would not receive a credit unless her family earns at least $25,000 yearly. Parker said her husband William earns about $19,000 in a printing shop.

When informed that her family might qualify for at least a partial credit toward her daughter's tuition, Parker said, "I sure would favor" any law that helps pay even part of the bill.

But fellow parishioner Elizabeth Brown, a 65-year-old great-grandmother from Capitol Hill, was opposed. At first, she said, she supported the idea because "we have a lot of gifted children in the community, but parents can't afford to send them" to good private schools.

Brown said that after considering the claim of D.C. city officials that the tax credit would result in lost revenue, however, she was swayed to oppose the measure.

"We have closed enough schools already," she said, "and if the city loses more money, then you'll be cutting off your nose to spite your face."

But another St. Benedict's parishioner, Francina Grinnage, a medical technologist from Northeast Washington, plans to vote against the tax credit because she believes parents will be encouraged to "pull their kids out of the public school, and then the public school will go down to nothing. They'll lose kids and then they'll lose teachers."

Grinnage said that her daughter, Tynesia, 10, had attended a private school, but did not enjoy it or excel there. Tynesia, she said, now is doing better at Brent Elementary in Southeast.

Many St. Gabriel's parishioners, who live in the Petworth section of Northwest, said they also want the tax credit because they have tried the public schools and found them wanting.

Ada Pollard said that her son, Aaron, had to transfer from Roosevelt High School to Mackin High School, staffed by the Brothers of the Holy Cross, a Catholic order, because she felt that the students at Roosevelt were "out of control . . .breaking into lockers, smoking herb." Pollard, herself a graduate of the D.C. schools, said she found discipline at Mackin far superior.

Plummer said he became disillusioned with public schools when his younger brother was attending McKinley High School and he found that llth graders there still were doing spelling lessons.

He said that another brother transferred from St. Francis DeSales School, where he was making a C average, to Taft Junior High School and got mostly Fs his first semester for cutting classes.

"You see, you couldn't goof around at St. Francis DeSales like you can in the public schools. He told me the reason he was cutting classes at Taft was because they were doing work there that he already had at St. Francis," Plummer said.

In the last school year, 12,l74 students were enrolled in the city's 34 Catholic schools, where tuition ranges from $604 to $950 on the elementary level and from about $1,200 to $1,800 in the high schools.

About 75 percent of the elementary school students and about 50 percent of the high school students are black. While a large number of D.C. Catholic school students actually live in the suburbs, the vast majority live in the city and their families therefore would be eligible for some sort of credit.

Virtually all of the city's Roman Catholic schools are filled to capacity, and most have waiting lists.