LONG AFTER twilight, a jazz singer almost went unnoticed as a crowd of about 250 milled about inside a sprawling Northwest Washington estate for... a PTA fund-raiser over cocktails? Only in Washington could a PTA, like this one at Horace Mann Elementary School, raise $160,000 in one November night without selling a single doughnut.

These days it takes the shrewd thinking of a Wall Street analyst to finance PTA efforts in many schools. Tight school budgets and staff cutbacks are prompting some Washington parent groups to take matters into their own hands.

If the school administration is too cheap to hire an art or science teacher, the parents bring in their own. If the school board considers a part-time nurse a frill, the parents hire their own. If somebody upstairs believes a kindergarten teacher actually can teacher 25 students without any help, the parents pay for their own aide.

Take a look inside Lafayette Elementary School in Northwest Washington; walk into classrooms with parent-hired teachers and this kind of thinking seems perfectly sound. Instead of standing on the sidelines watching the quality of their children's education decline, Lafayette parents are working to fill in the gaps with their own money. Ohe of the gaps they have filled is in the school's art program.

On a recent morning, part-time parent-hired art teacher Laurie McLaughlin was supervising sixth graders who were slicing up bathroom tiles for printmaking. Never mind that this year McLaughlin will earn only about $8,500; she says she doesn't care. She's so sold on the young Lafayette artists that she has stated skipping lunch to organize a children's art club.

According to Winnie Blatchford, president of the Lafayette Home School Association, the parent group is picking up the tab for McLaughlin's salary and making payments for social security, unemployment compensation and workmen's compensation. This year, with $33,000 in the HSA budget, Lafayette parents have also hired an assortment of part-time professionals -- a science teacher, nurse and clerical assistant. But all of them, Blatchford said emphatically, work for the school, not the association. "We [the parent group] stay out of the classroom and say, 'Work under the principal's guidance.'"

Almost every day between 15 and 25 youngsters visit the school's HSA-hired nurse, Anne West. Sometimes they're just looking for someone to wipe away the tears and hug them.

"It's like having your mother here, someone you can turn to and say, 'I hurt,'" said Blatchford. "I don't know what these kids would do if she wasn't here -- the school would have to send them home."

Recently principal Sandra Nesmith was informed that District health officials will stop sending a D.C.-paid nurse who has been coming to Lafayette once every two weeks. Nesmith fumed, "Just because the parents are paying for a part-time nurse, we shouldn't be penalized. They said there were schools with no [nursing] service, and it's hard to argue. But it isn't fair. Schools west of the park are always being criticized for having more."

The disparity between Washington's wealthy and poor schools is as old as the Washington Monument. It's a sensitive subject; one that both parents and administrators, tiptoe around, because for many years the poorest schools were hardest hit by budgetary whims and parents couldn't make up the lost money. Finally, the scales started to shift in October when the Washington Lawyer's Committee, a private nonprofit organization that specializes in civil rights litigation, threw its weight behind a project to raise money in Southeast Washington schools.

For low-income parents weary of passing an empty hat at PTA meetings, it's a windfall. Two corporations, Chesapeake & Potomac Telephone and Westinghouse, have agreed to give parents $2 for every $1 they raise at nine Anacostia schools. By the end of the year, each school may have between $5,000 to $8,000, if the Lawyers' Committee Parent Group Support Fund has its way.

"Anacostia parents have been let down so many times by people who said they would do something to help them. They had stopped listening until this program started," said Linda Moody, an Anacostia parent who is the fund's president. "So much needs to be done... we're talking about a place where some children are kept out of school because they don't have coats or shoes to wear."

Away from the silkier world of big-time PTA fund-raisers. Southeast Washington parents in years past often rallied around survival issues: finding shoes for desperately poor children; patching the cafeteria ceiling that flooded everytime it rained or painting over the walls of depressing-looking classrooms. With these kinds of needs, it was difficult for many to think about buying a computer for the math class or hiring a teacher's aide.

"Many of these parents didn't have experience in advocating their own position in budget fights. They can't write checks for $50 to join the PTA; the money just isn't there," said Roderic VAO. Boggs, executive director of the lawyer's committee. "Now at least they have a fighting chance."

What's encouraging about all of this is that it's not a "haves" vs. "have nots" fight for the almighty budget dollar; there's not a price tag on parent involvement in the schools. It's impossible to measure a PTA's impact by how many dollars are in the bank, because in many schools parent volunteers are as devoted as full-time teachers.

But certainly the business of fund raising is taking on new dimensions. Parents at Murch Elementary School in Northwest Washington took over the New Zealand Embassy last March for a fund-raiser. They managed to pull in $12,000 in one night after auctioning off weekend stays at resorts, day-long sailboat outings and original oil paintings.

"We either raise the money ourselves or do without, and nobody wants to do without," said Kay Huggard, president of the Murch Home and School Association. "Parents are constantly saying. 'That's something the District should provide,' But the fact is, it doesn't. We pressure the school district for more money, but in these times of tight money everything is being cut back."

With $34,000 in this year's budget, Murch parents hired a part-time science teacher, nurse, pre-kindergarten aide and clerical aide. And like other upper-middle-class schools such as Lafayette, Murch parents are contributing $1,000 to the Parents United for Full School Funding, a lobbying group organized last year to pressure city officials to put away the ax during budget sessions.

"The more parents pay, in terms of providing things normally paid for by the school system, the more they will be called upon to pay," said William Brown, president of the D.C. Congress of Parents and Teachers. "It's my feeling that it is the parents' role to demand the system to deliver the education it's legally required to."

Parent groups are increasingly puzzled over this dilemma: Do they encourage more cuts by plastering over the holes in their children's education with their own money? Or do schools that quietly accept budget cuts only convince administrators that science and art teachers and nurses aren't essential?

Perhaps without even realizing it, parents are moving into unexplored territory by financing items like air conditioning in such wealthy school districts as Fairfax County. At Wakefield Forest Elementary School, the PTA has spent the last few years selling flower bulbs and popcorn and raffling quilts to raise $7,500. And parents are still nearly $13,000 short of paying for air conditioning in six classrooms in an older section of the school.

"PTAs are going to have to raise money for whatever simply because there isn't enough money to go around. Besides, I think it gives parents more of a vested interest in the school," said Wakefield Forest PTA president Linda Bardot. "Now they can point at the school and say, 'This is what we have done,' not 'This where we send the kids six hours a day.' There is a feeling of community."

The cookie-and-doughnut route to high finance is a long one, but the majority of PTAs in the country are still struggling along that way, national PTA officials say. That's not surprising, looking at the drastic decline in PTA membership during the last 20 years. Six million parents -- half the number in the late 1950s -- belong to parent-teacher associations; and that number is declining primarily because schools' enrollments are dropping. Also, as mothers enter the work force in increasing numbers, there are fewer people who have the time for the volunteer work which has been the backbone of PTA activity.

In the Washington suburbs, there doesn't seem to be the same urgency among PTA organizers, perhaps because only the D.C. school system laid off 1,000 employes last year. Lucy Barnsley Elementary School in Rockville is fairly typical of many suburban PTAs. This year -- if parents sell enough T-shirts and baked goods and books -- the PTA may raise about $1,200 to help teachers buy classroom supplies.

Comparing fund-raising efforts is futile, but by any measure Horace Mann Elementary School's money-making theories are intriguing. After taking in $16,000 -- minus $4,000 for expenses -- from a silent auction in November, the PTA hired six part-time classroom aides. But even in an upper-middle class neighborhood, this kind of fund raising is exhausting, parents said.

"It's very, very difficult to get people to bid enthusiastically after they have paid $25 a person just to get in," said Judy Wood, co-chairman of the fund-raiser celebrating Horace Mann School's 50th anniversary. "Originally, we were dreaming that we would make $20,000 to $25,000 and put some of it into a growth stock or a mutual fund to hedge inflation. Now we'll just have to wait and see."

The high finance of PTA fund raising may be about as exciting as a school bus full of tax consultants, but it pays off. As one parent joked, if PTA promoters can balance their own checkbooks without a deficit, "Maybe we could all get together and hire a math teacher for the D.C. budget analysts."