The letter, based on a D.C. elections board list of campaign contributors to City Council Chairman David A. Clarke, went out to 800 Clarke supporters last month and hammered home one theme: The public schools need more money.

But the message didn't come from the council chairman. It was mailed by the 800-member lobbying group called Parents United for Full Public School Funding, as part of a systematic effort that has urged church leaders, ward organizations and community groups to pressure the council to vote for more school funds in the fiscal 1984 budget.

"We are writing to call your attention to the critical need to secure Council adoption of a fiscal year 1984 school budget of at least $336.5 million," said the letter to Clarke's supporters. "If you agree, we urge you to contact Dave and express your opinion."

Since Mayor Marion Barry proposed a school budget of $318.5 million last month, Parents United has spent $1,900 to mail out its own budget analysis, a fact sheet that outlines what cuts in programs and personnel would have to be made with the mayor's budget mark, a guide that shows what services should be available under the current year's budget, and mailings that supplied the dates of City Council public hearings and the telephone numbers of council members--all with a rented typewriter, tape and the help of a printing firm, said Parents United member Susan McDonald.

In conjunction with the D.C. Congress of Parents and Teachers, Parents United also mailed 45,000 notices to parents urging them to call council members and testify at budget hearings, said William H.L. Brown, president of the Congress of Parents and Teachers. Letters were mailed to 100 of the city's church leaders and the city's advisory neighborhood commissioners.

Since December, Parents United members have met with City Council members and several of the city's PTAs, and have appeared on television programs such as News-Center Forum and at community-based organizations such as the Ward One Council, said McDonald. The group raised funds recently by buying tickets at group rates for a showing of "Gandhi" at the Uptown Theatre, and its budget is now $7,000.

From an inauspicious beginning as a handful of parents upset over widespread teacher layoffs in 1980, the group has matured into an influential organization that helped fight for a substantial budget increase in the current fiscal year and has now set its sights on increasing Barry's proposed fiscal 1984 school budget. The way to accomplish the group's goal is to involve as many people as possible, members say.

"The reason for getting people involved is because the community is no stronger than its commitment to education," said Parents United president Phyllis Young, a Ward 4 resident who works as a manager of highway safety programs.

"We are going to knock on the mayor's door and deliver a message, a Chinese proverb: If you are planning for a year, sow rice. If you are planning for a decade, plant trees. If you are planning for a lifetime, educate a person," said Young.

There is no compromise in the flyers and fact sheets and independent budget analyses filled with warnings of doom circulated by Parents United in recent weeks. The group contends, among other things, that if teacher layoffs were the sole solution to the $18 million difference between the schools' request and Barry's mark, 850 teachers would receive pink slips--a figure that doubles layoff claims by the school board itself.

That disturbs some city officials such as Clarke, who views the City Council's position as one of being caught in the middle of the annual budget battle between the mayor and the school board.

"I appreciate their advocacy and intensity," said Clarke. "But I think they sometimes do a disservice to their own cause by saying that anything less than what the board requests will result in teacher layoffs when there are obviously other adjustments that can be made."

But Board of Education President David Eaton views Parents United as "a valuable ally." And Parents United members are convinced they are correct.

"The bottom line is that the future of the city depends on the education of our children," said Mike Prival, the secretary of Parents United, "and the education of our children depends on full funding of the schools."