KANSAS CITY, MO. -- The early-morning playground scene at George B. Longan Elementary School is exquisitely ordinary. Children, most of them inner-city blacks, caper across the asphalt, absorbed in the rituals of tag and kickball. Their cries carom against a red brick building indistinguishable from a thousand other schools in a thousand other towns.

But at the bewitching hour of 9 a.m., a bell summons the children inside, and the Longan School is transformed. The gym becomes the salle de gymnastique, the restrooms are labeled messieurs and dames and the cheerful man with a mop is not a janitor but the concierge.

In Room 2, Belgian teacher Muriel Desbleds leads her second graders through the previous night's homework, entirely and joyfully en francais. When two little girls giggle inattentively, Louisianne Roskam, a teacher's aide from the Seychelles, whispers from the back of the room, "Tournez vous devant et ecoutez!" As commanded, they turn around and listen.

Even a casual observer, hopelessly unlettered in French, can see that L'Ecole Longan is alive with learning. The school is a small manifestation of a vast social experiment, perhaps the nation's most ambitious, expensive and controversial desegregation plan. At a cost expected to reach $700 million by 1992, a federal judge has commanded the predominantly black Kansas City district to make itself so innovative, so irresistibly competent that white suburbanites voluntarily will send their children into the city for an education.

Last month, the Supreme Court upheld U.S. District Judge Russell G. Clark's authority to order higher taxes needed to underwrite his sweeping overhaul of Kansas City schools. But five years into Clark's plan, results are mixed at best. Dozens of schools have been refurbished or rebuilt, and the student-teacher ratio has dropped from 35-to-1 to 22-to-1.

More than half of the district's 77 schools have been converted to "magnet" programs ranging from full-immersion French, German or Spanish, to science and mathematics, to performing arts, to "computers unlimited." Once uniformly dreadful, Kansas City public schools now range from respectable to outstanding.

But critics decry the experiment as a vestige of a Great Society-era impulse to treat social ills with massive doses of money. They see gold-plating in the district's new planetarium, 25-acre farm, art gallery, television studios, dust-free diesel mechanics laboratory and model United Nations -- replete with wiring for language translations. Some local residents object to a court-imposed doubling of the local property-tax rate, while many Missourians outside Kansas City resent a court-imposed requirement that the state pay three-fourths of the bill.

Test scores have improved only modestly, and less than 3 percent of Kansas City's 34,000 pupils have transferred from the suburbs or private schools into the district, which remains 75 percent minority. Blacks comprise 31 percent of the city's population.

Those supporting the plan counsel patience. Success in Kansas City, they believe, could suggest a viable way to revive and desegregate big-city schools without forced busing.

"For 35 years, since Brown v. the Board of Education, we've been struggling to find a solution to a national tragedy," said Arthur A. Benson II, attorney for a group of students who filed the initial desegregation suit in 1977. "One of the things this experiment in Kansas City will show is whether money makes a difference in improving education. Failure here could have dire consequences for the future of desegregation and urban education in the country."

"In many ways," added Eugene Eubanks, chairman of the court-appointed Desegregation Monitoring Committee, "it's big-city education on trial."Rebuilt From Playground Up

Since 1967, when 75,000 children attended Kansas City schools, enrollment has plummeted. White flight, race riots and a teachers' strike accelerated the decline and in two years, 1974 and 1977, the city lost one child in five, according to Superintendent George F. Garcia.

Buildings, books, furniture and morale also deteriorated to the point that Judge Clark found them "literally rotted." Beginning in 1969, the year in which black students outnumbered whites for the first time, Kansas City voters refused eight times in 17 years to approve an increase in the school-tax levy. In 1984, after a long trial, Clark, 64, ruled that the district and the state operated a segregated school system in Kansas City. Nine months later, he issued the first in a series of remedial orders.

A native of rural southern Missouri, Clark had been on the federal bench only three months when he received the Kansas City schools case. Once describing himself as a conservative "except in civil rights matters," he rejected the remedy of a Boston-style forced-busing plan; instead, he set out to rebuild the district from the playground up.

Clark unilaterally raised the tax levy and ordered the state, which had a long history of encouraging and even requiring segregation, to pay most of the costs on the theory that "the person who starts the fire has more responsibility for the damage caused than the person who fails to put it out."

Similar efforts to lure suburban students into the city had been tried elsewhere -- Eubanks cites Milwaukee and St. Louis as examples -- but never on the scale envisioned by Clark. As an appeals court judge put it, "The remedies ordered go far beyond anything previously seen in a school-desegregation case. The sheer immensity of the programs . . . are without parallel in any other school district in the country."

By next year, all secondary schools and half of the elementary schools will be "magnetized." Clark has decreed that each magnet school must be 60 percent minority and 40 percent white, some immediately, others incrementally. Only about half have met his quotas.

No one denies that the schools are better academically. North Rock Creek-Korte Elementary School, for example, has been a magnet for three years. Stressing environmental science, it has achieved the 60-40 split and has lured several dozen pupils from outside the district with such features as a science lab with an elaborate weather station, frequent field trips, a large greenhouse with hundreds of plants, extensive before- and after-school programs and a log cabin used variously to demonstrate a slave cabin, a pioneer's hut or a farm house. "We don't read about it, we do it," Principal Cynthia Kupka said. "If the textbook talks about candlemaking, we make candles."

Tami Jenkins, who lives east of Kansas City in Independence, said she "took a lot of criticism from my neighbors when they found out I was sending my kids to this school. They think that I'm exposing my kids to unnecessary dangers and problems. I think the people who say that are speaking out of ignorance."

Cathy Mousel, who sends her two children to North Rock Creek-Korte from Independence, added, "There's a lot of pressure on us as parents from people who say, 'Why would you want to send your kids into a school where there's more black than white?' "

For many suburbanites, however, loyalty to local schools runs deep. "I do not personally know anyone who is sending their children to a magnet school in the city," said Karen Miller, who has a son in a North Kansas City high school. "You'd have to travel on the interstate and cross the river into Kansas City, and it would have to be an exceptional school to make you want to do that."

Perhaps the most controversial plan approved by Clark is the rebuilding of Central High School, now virtually all black. When a completely new Central opens in September 1991, the resurrection will have cost an estimated $32 million, twice the average price of a new high school of similar size. Students can select either the "computers unlimited" magnet program, in which each pupil is to have a personal computer, or the "classical Greek" program, which is to emphasize the Hellenic ideal of "building a citizen, a whole person, physically and mentally," as Assistant Superintendent Art Rainwater put it.

To nurture athletes, Central will boast a 50-meter indoor pool, handball courts, gymnastics rooms and other elaborate facilities. Students will study Greek language and drama, classical authors, debate and more traditional subjects under teachers versed in the Socratic method. Missouri Gov. John Ashcroft (R) is credited with dubbing new Central High "the Taj Mahal," a moniker that many Kansas Citians use with pride.

"Such facilities," Clark wrote, "are necessary to attract non-minority suburban students to the inner city to accomplish the difficult task of desegregating Central High."Recruiting Problematic

Attracting white students has proven more difficult than rebuilding schools. A recent offer to conduct short seminars on Kansas City's magnet schools for employees at 3,000 companies in the metropolitan area was "a complete failure," according to attorney Arthur Benson. The district's recruiting efforts in general have been criticized as incompetent and ineffectual.

"Public school educators have not been trained to recruit clients to their schools," Superintendent Garcia responded, adding that, after coming to Kansas City in 1987, he initially was preoccupied with the growing pains of a district whose annual budget expanded in 18 months from $110 million to nearly $300 million.

With students given a choice in selecting schools, transportation within the sprawling district has been exasperatingly complicated. "We can have a street with 50 kids living on it, and they can literally go to 50 different schools," Rainwater said. "The logistics of getting the buses to take them to the right places is a nightmare." As an incentive, the district will send buses or taxis to suburban doorsteps; within the district, more than 700 school buses crisscross the city.

Some Kansas City blacks voiced qualms about losing control of a newly enriched school system to whites who seemed uninterested when the district was poor. Another Clark plan, to persuade suburban districts to accept inner-city blacks voluntarily, also has provoked antagonism from blacks. "Why should we transfer to suburban, white-dominated schools and let white private and suburban students take our places?" community activist Clinton Adams Jr. asked recently in the Kansas City Star.

If Clark truly wants to integrate Kansas City schools, some educators suggested privately, he eventually must merge inner-city and suburban districts and order comprehensive busing. But those who believe most ardently in the current experiment are a long way from abandoning it.

"To create a level playing field, this district had to be raised to the level of the others around it," said Sue Fulsom, who has served on the school board since 1982. "There was just too much to do here to expect that it could be done in just five or six years. . . . I think we've got 10 years to go before we have a school district that we all can be extremely proud of."

Benson agrees, saying, "Ten years from now, we'll know whether the social problems of an urban school district, including desegregation, can be solved with money and hard work."

Staff researcher Lucy Shackelford contributed to this report.