Backstage - An old fish market turned into a cinema museum, Backstage serves Veal Ginger Rogers (with lemon and ginger), Donald Duck (with strawberry glaze) and sometimes rents extra chairs to accommodate the crush of 150 brunches in three hours in a 30-seat restaurant.; Lickity split - One of the first of the new genre of restaurants, it has recently changed owners. Waitresses in jeans and sneakers serve spring rolls and chicken teriyaki on mirrored tables amid flowers, plants, trees and waterfall. Downstairs is rock music, upstairs classical. Bogart's - An Art Deco hotel restaurant started by Jay Guben, it features coulibiac of salmond, planked seafood, bouillabaisse, roast beef, chopped sirloin and a friendly bar. Wildflowers - The menu stretches from Dutch to Greek, but the central feature is "The Grand Salad Buffet," a salad bar so posh it includes Bibb lettuce and brie. Two admired French Restaurants in Philadelphia are also very small, one a spinoff from the other (perhaps disagreeing on which spin off from which), and committed to purism, Gallic embodiments of the Philadelphia renaissance. They are Le Bec Fin (which takes no credit cards in payment for its $35 fixed price classic, multi-course dinners) and La Panetiere. Under the Blue Moon - Batik tablecloths and appliqueed wall hangings set a casual, artistic, handcrafted tone to this small restaurant, owned by two Restaurant School graduates. The menu runs to sole with macadamia nuts, port stuffed with apricots and walnuts and sauced with sour cream and lingonberries, chocolate strawberry pie and cappuccino hazelnut ice cream. The music is classical, the mood meant to be like a home dinner party. Maxwell's Prime - Jay Gubenhs newest, a steakhouse, is strictly limited to grilled meats, prime, well-aged, and high-priced. Among Philadelphia's other noteworthy new eating places are Corned Beef Academy, a delicatessen started by a Restaurant School graduate, Piccolo Padre, a new Northern Italian family restaurant, Marrakesh, a Moroccan restaurant, Conversation, a pastry and tea room, and Mostly Muffins, a specialty bakery.

Looking into a crystal flute glass I see restaurants proliferating. But I don't need a crystal crutch for such a prediction. Restaurants always proliferate. The question is: What kind? And "McDonald's" is only the easy part of the answer. What else? What is going to happen at the upper rungs of the restaurant scale?

Every field has its bellwethers. Political pollsters have certain small towns they rely on for statistically accurate predictions of election outcomes. Doctors take pulses. As for restaurants, I am looking at Philadelphia.

Philadelphia? That city that gives you two chances to get off the train before New York, and you never bother? The city with the nearly official joke: First Prize, a week in philadelphia; Second Prize, two weeks in Philadelphia?

Yes, Philadelphia. The city with 150 new restaurants in the last three to five years, nearly all of them surviving. The city where even the porno bookstores advertise "Free coffee and homemade cookies at all times."

Philadelphia, culture watchers should know by now, didn't stop crafting revolutions with ben Franklin. This century, Philadelphia has been the pulse of cultural revolutions, and restaurants are phase four.

First, at the turn of this century, it was Thomas Eakins, the instigator of the art renaissance that created the Philadelphia Museum School. A half century later, handsome, patrician Richardson Dilworth swept a broom through the city and then the state government. Not long after, Edmund Bacon, tall and austere, built the city planning commission - and the city - into a physical model for revitalizing America's cities and towns. Then came Jay Guben, a pudgy and unlikely looking guru, working his way up from peeling potatoes to master mind a restaurant renaissance.

Like most revolutions, the Philadelphia culinary revival didn't exactly start with Guben. It started on South Street, a neighborhood of junk stores and junkies, antique shops and wedding gown wholesalers, crawling with police and police dogs and - if truth be told - not too different from the way it looks today, except that now South Street has two dozen new restaurants as well as a reasonable facsimile in miniature of San Francisco's Ghirardelli Square.

The first cell of this most savory of revolutions was an ice cream parlor called the black banana. The Black Banana hired art students as sundae-designers and concocted the confections with a passionate purism. Customers lined up around the block. Consciousness was raised. Palates were readied for liberation.

The stage was set, and Jay Guben entered from the left. Guben was one of those '60s inventions who veered from ambitions as a golf pro to political activism; he acquired a master's degree inconflict management and went on to run an urban renewal project in Cincinnati. Then, veering again, he signed on as a potato-peeler in Pennsyvania's highly respected Coventry Forge Inn, an assignment interrupted by a six-month stint in the hospital after a car accident; in the hospital he was reborn as a restaurateur. Guben and Vicki Rensen, who had also worked in Coventry Forge Inn's kitchen as pantry chef and later as second chef, pooled their minimal assets in 1971 to open the restaurant of their dreams, Les Amis, a small establishment (fewer than 80 seats) with a commitment to quality without pomposity. The place proved to be a learning laboratory for Rensen -who was raising six children and had little professional background other than a housewives' course in Copenhagen that she described as "castle management"-and Guben. Guben found that his skills were "starter skills," and lost interest once the restaurantwas running smoothly. He left within a year, retaining some financial interest, and gathered six other people with $2,000 each to open a 50-seat restaurant called -and open-Friday,Saturday and Sunday. According to Guben, they opened in four days. "The problem was, we did business. We would have handled a failure very well. We were not ready for success." Within six months, with lines forming to wait for tables, one partner bought the others out for $35,000. Within the next five years, Guben opened nearly a dozen restaurants (Morgan's, an English pub; Upstairs Downstairs, Caribbean, since changed to Avati; Set Table, a "gourmet kosher restaurant," his only admitted failure; Aunt Sylvia's Cheesecake, which folded only because Aunt Sylvia made enough money to move to Florida; Bogart's, amodestly successful foray into hotel restaurants; and more). Guben found the locations, developed the concepts,designed the physical facilities, hired the staffs, arranged the financing, then got bored.

In the meantime, the news of restaurant gold spread, and the fever took hold.

On South Street came Lickety Split, famous for its second-floor waterfall, chicken teriyaki and Bulgarian yogurt soup, for which it made its own yogurt. Then came Steve Poses, opening the Frog, an 85-seat restaurant that now grosses $1.2 million a year, busier per seat than Manhattan's Tavern-on-the Green, smoking its own fish and serving dishes unheard of in Philadelphia: duck salad with fresh figs and peaches, for instance. The restaurant revolution had its leaders and its splinter groups. Xavier Hussenot of the Black Banana was the radical; once his restaurant grew in size and stature and left ice cream parlor tricks behind, he moved it to Skid Row, a new challenge for an eatery where the average dinner check is $25 to $35. His inclination is towards formality, with tableside flaming of the $15 duckling. Poses, at the other extreme, has now opened what may be the world's most ambitious cafeteria, the Commissary,where ten different wines are avaiable by the glass, and fish pates are regulars on the cold buffet. Poses, like Guben, came out of the peace movement and city planning. He sees restaurants like his-individualistic and dedicated to fodd as a craft-as "personnal urban renewal." Unlike Guben, he finds challenge in the maintenance of his two restaurants. "Opening is the easiest part," Poses believes. The hardest part is retaining the competitive edge, keeping the staff involved in a continuous cultural revolution, moving people around to keep them interested.

The new restaurants of Philadelphia, serving Americanized versions of everything from Caribbean fruit soup to Congolese steak, have developed a fully equipped restaurant society. Besides customers who never before surfaced, who only became interested in dining out once the dining possibilities became plentiful, the restaurant renaissance now has a school to reinforce it.

The Restaurant School-and in the consciously unassuming style of the restaurant trend, that is its name-was started by Jay Guben, with education director Anita Simon an early draftee. Four years ago it opened with 12 students, eight of whom lasted to graduation. Its aim is to teach a student to own, manage and operate a small,fine restaurant. Now that there are 78 graduated and a current class of 36 students, the methods have been refined but the goals remained solid. In the ten-month course the students learn cooking-"enough to tell if your chef is screwing up," according to Guben-but the school devotes nearly equal time to business management and to dining room management. Most of the school hours are spent actually running the school's restaurant, the concept of which the students devise anew each month. The restaurant is open to the public, serving $6.50 fixed-priced dinners.

Originally the school was designed for people who wanted to change careers mid-life, and attracted social workers, insurance agents, women starting careers after divorces. But the students have been getting younger, and now there is a predominance of straight-from-school applicants.

Nevertheless, the Restaurant School is no traditional trade school. The first day the students visit restaurants, then critique them. Lesson one: Their critiques are mostly opinion, and the audience learns more about the critic than about the restaurant. Lesson two: "We went in such nice people and came out monsters."

Thereafter, they learn what it takes -besides $3,640 tuition-to gain the fundamental of the restaurant business. They study concept and design, financial analysis, bookkeeping and budgeting, taxes and licensing, bank relations, choosing professional services, analyzing leases, personnel and customer relations, wines and liquors, food presentation, kitchen layout, table settings. But what they remember, what is the most important lesson, according to graduates, is self-confidence, the sense that they can do it. Confidence and contacts are continually cited by graduates as the greatest value of the school. The school is described as a survival handbook, with the most important element of survival being the ego. While 20 percent of the students drop out, in order to graduate, according to Guben, "All you have to do is breathe and attend class; and at least Anita will be supportive of you."

A visit to the school, however, reveals that the students hardly have time to breathe, and peer group pressure as well as the faculty standards keep goals high. Students are taugh through experience that running a small restaurant means working 14 hours a day, six days a week, with the hopes of earning up to $25,000 a year within a year or two of opening a successful restaurant.

The school teaches its students "to do things as well as they will ever need to know," said Guben. "We have people bone trout when they may never see a trout again." Shortcuts are anathema. And years later, the students still revere cooking teacher Tom Hunter.

In the townhouse basement kitchen, students and Hunter, all of them in sneakers and sandals, cutoffs and overalls, bounce a brief argument across the sloping floor.

"It is that artificial vanilla Beverly bought."

"Oh, Beverly!"

Beverly winces. "I know. I've been taken."

These students learn a Philadelphia brand of perfection.

Nearly one-fourth of the Restaurant School graduates own restaurants, mostly in Philadelphia. Another fourth work for them. Philadelphia media describe dishes as "Restaurant School eclectic," or "a traditional Restaurant School recipe." Certain symbols identify a restaurant as a Restaurant School spinoff. First, there is the water pitcher with lemon slices floating in it. An early teacher, Hans Bachler, "thought it was chic because Philadelphia water is so lousy," revealed Guben. It stuck. Restaurant School spinoffs make everything from scratch-the puff pastry, the mayonnaise. They use a lot of fruits on the menu, often combining them with meats or fish, as in flounder with grapes, bananas,cantaloupe and dill. Everything that can be wrapped in a crust will be. Vegetables are bright and crisp, honored on the plate. And pistachios are rampant. "Pine nuts may be a splinter group," mused Simon.

The restaurants' styles are casual, their service correct in its execution but informal and friendly in its approach. Menus are short and seasonal. Visual impact is important in the food; dishes are garnished with color and flair and enough cherry tomatoes to have given a boost to the tomato industry. There is an emphasis in the unexpected-an odd juxtaposition of spices, or soups with a surprise twist. Sauces are the weak link, lacking finesse, but desserts compensate, being the most professional part of the cuisine.Tom Hunter has found that menus start out too involved with the concept or theme, but later relax. Simon describes the Restaurant School spinoff -the boutique restaurant, the New Wave restaurant, as the genre has been named-as studied avant-garde,falling short of the gutsy or truly authentic, but exciting, individualistic and good-natured.

The new boutique restaurants often seem like families so strenuously does the management devote its life to the business. Such long hours are hard on a spouse not involved in the business, so frequently the husband and wife both join in the operation. Similarly business partners often end up living in communes or developing familial relationships. The cook or waiter becomes like a son or daughter. And in Philadephia restaurants, unlike Washington restaurants, the relationships are long-term. Turnover in staff is low, except for dishwashers. $

The restaurant family links with an extended family. Philadephia's New Wave restaurants have their feuds and clans, but they are deeply involved with each other. They share information about suppliers and exchange customers and staff, evenas they compete to serve the first raspberries of the season.

Steve Poses sees restaurant jobs as "What the '60s people do in the '70s." One wonders what they will do in the '80s. Youthful is an apt description of Philadelphia's boutique restaurants, with all the appeal and disillusion that involves. Nobody knows, however, whether they will stick around long enough to age gracefully. It is not a matter of success; none of the students' restaurants has been known to fail. It is a matter of commitment, the question of whether boredom and routine will sabotage success. Restaurateurs who have graduated from the Restaurant School don't seem to look beyond the next five years. At their worst moments they talk like Georgianna Crumback on the eve of her opening the Restaurant for the summer: "I've just about had it with a small, fine restaurant. It is hard. I'd like a small tap room."

The Restaurant School becomes a way of life, at least for those students who stayin Philadelphia. They work with their ex-classmates, often live with them. They hire Restaurant School students. They borrow money from their instructors. They run Guben's newer and newest restaurants.

Guben's restaurants have served as halfway houses for graduates. In fact, one, Vincenzo's, was set up to be managed by a different graduating group each year. Other restaurateurs take Guben's success with a grain of salt, explaining it away as Guben just changing the name and bringing in a new group of students every time a restaurant is in danger of failing. Xavier Hussenot, one of the owners of the Black Banana and a former teacher at the Restaurant School,sneered that students "had no choice but to work for Jay after they have been to the bank and back." He criticizes the Restaurant School spinoffs -"too many dry spices in the food" and "they change chefs whenever they have ups and downs"-charging that the school's labor pool allows the restaurants to heal themselves as they could not in a less protected situation. But more basically, he considers the graduates spoiled, wanting to run a restaurant but not ready for it, needing more experience.

Many graduated do go to workin other restaurants while they plan their own dream restaurants. Several have devised creative solutions to startup problems, getting minority loans as women, or persuading the city government to allow them to open a cold lunch terrace in an abandoned water works. One graduate is working as a chef and caterer as he builds his pate factory.

Steve Poses and Vicki Rensen, like Hussenot, think apprenticing is the best way to learn how to run a restaurant. The problem they see with the Restaurant School is that it aims to train owners rather than employees and thus does not serve as a labor pool for other owners. They, therefore, prefer to train their own workers. As Poses put it, "School isn't enough. It is a good foundation and overview, but you have to go and dig in."

Whatever the Restaurant School's role is in its students' careers or in providing an employe pool, it and Guben have substantially increased Philadelphia's restaurant pool. Graduates hold major positions in about 20 local restaurants, half of them startedby graduates.

Their influence now is spreading beyond Philadelphia. Graduates have opened restaurants as far off as Colorado and Maine. Guben's counsel is sought by restaurants around the country; this falls, two Washington enterprises called Guben about the possibility of his opening a restaurant here. The Restaurant School's graduates have worked at the Madison Hotel and the Big Cheese, and one plans to open a restaurant in Annapolis. Clyde's has been in touch with the school, seeking chefs.

The Philadelphia renaissance itself is spreading its gospel. The Fish Market, an intensely successful combination fish market and restaurant, looked into Washington for a possible branch restaurant. And more subtly,Washington's restaurants are looking for models. Owners of the American Cafe toured New York and Philadelphia restaurants to see what is new they could learn. Manhattan's SoHo has been sprouting restaurants, too, but they reported that in Philadelphia one finds the newest trends. Philadelphia's restaurants are less professional than New York's, but they are experimenting with the latest merchandising techniques such as retail outlets connected to restaurants, and high-quality self-service. They were impressed by the individuality, by everything's being prepared on the premises and by the emphasis on freshness. Their main criticism of the Philadelphia genre is its faulty quality control. As one American Cafe owner put it, "Philadelphia is confirming to us that it is worth it to do what we are doing." What they are doing is building a central kitchen to cook everything from scratch for their restaurant and restaurant-to-be.

Like any idea whose time has come, the small, individualistic, high-quality American restaurant is sending shoots up in Washington, too. The Big Cheese alone has had its spinoffs in the Gandy Dancer. Fiddler's and Gadsby's Tavern. . .for a start. The Wolin family's Hot Diggity Dog branched into Patent Pending,2091/2, and now at least two other restaurants-in-process The Tabard Inn and the Broker are American restaurants the Restaurant School would find familiar. The Bread Oven has pioneered locally the bread bakery-restaurant combination, soon to be followed by Vie de France's new restaurant. Mitch and Linda Berliner's food stand at the Bethesda Farm Women's Cooperative has developed its carry-out cooking to near-restaurant proportions, as did Georgetown's Gourmetisserie with its TV tables set in the window.

In Philadelphia and in Washington, some of the new, small, personal, imaginative restaurants are ethnic. But more are American, adapting foreign cuisines but beginning to present a modern American cuisine to the public, just as the champagne raised to toast their venture is more likely than ever to be American. CAPTION: Picture 1,Latest Dish-The four-story flour sifters remain in this ex-bakery, and the floors and walls are still white tile. Vegetables are steamed to order, lemonade freshly squeezed. The "continental menu" spans several continents, including stir-fried beef with vegetables, chicken amaretto and filet of beef served with crab imperial. Photographs by Bill Snead; Picture 2, Avanti-A Restaurant School spinoff, it serves Mediterranean food such as North African chicken pie, artichokes stuffed with salami and ricotta and scallop seviche with vegetables(pictured),in a sunny orange and dark wood setting with bare floors and cane-back chairs; picture 3, Restaurant School-The school's students operate their own restaurant, offering $6.50 fixed-price dinners and changing the concept each month.; picture 4, Black Banana- Art Deco elegance on two floors with the hundred seats lavishly spaced, the Black Banana flames its $15 ducks at the table, serves with formality and precision. Co-owner Xavier Hussenot taught at the restaurant School, favors the elaborate and unexpected like terrines of goose liver with frogs' legs and crab with orange cream dressing. Average check is $25 to $35.; Picture 5, Cafe Lafitte-The chef and owner are from the Restaurant School. Thirteen staff people serve the 60 seats in the lovely townhouse with tall windows and tiny balconies. Pastries are a specialty, along with homemade ice creams and sherbets. Main courses include smoked trout stuffed with scrambled eggs (pictured) and oriental shrimp salad.; Picture 6, Fish Market- This combination retail fish market and restaurant airlifts in its own snapper, pompano,salmon and lobster, cooks everything on the premises from seafood pies to pastries. The market and 130 seats (on three skylit floors decorated with flowers, brass and stained glass) are staffed by 100 fulltime employes, four of them just of boning fish. No meats are served, just seafoods: cold lobster with clams and fruit garnishes(pictured), scallops with hazelnut butter, rainbow trout sauteed with bananas and almonds and crab in pineapple shell. Prices are high, with main dishes starting at $8.50.; Picture 7, Commissary-A new self-service sibling to Frog, this may be the only cafeteria in the world that employs seven fulltime bakers (the heart tart, pictured,has become a trademark ), stocks 17 brands of scotch, 15 different brandies and sells 10 different wines by the glass. Daily food selections range from couscous to seafood strudel to galantines to a repertoire of 150 homemade soups. Sherbets are made in-house, as are mayonnaise and croissants. Coffee is ground fresh for each 12 cups. The bar is mahogany, tiles are handmade, the floor is inlaid with nine kinds of wood. And overhead is a cookbook library for browsing.; Picture 8, Frog-The blackboard menu features dishes like cold duckling salad with figs and peaches, fish smoked in the restaurant's own basement, and is upstaged only by the enormous bargain-priced wine list. Dishes, such as softshell crabs, are beautifully presented. Small, bright and busy, Frog prices average $14 a dinner.;Picture 9, Friday, Saturday and Sunday- Under the draped multicolor fabric ceiling rock music plays, and diners relax against pillows at banquettes. The menu on the blackboard lists three-meat salad, duck with leeks(picture) or curry sauce, spinach and fish pate, perhaps a cold beef salad with carrot flowers. It was started by a group including Jay Guben, with chef Tom Hunter of the Restaurant School, but was carried away by success, despite its lack of liquor license. Average check is $13.; Picture 10, 20th Street Cafe-Most of the staff in this 50-seat restaurant are from the Restaurant School. Except for a few stunning floral accents, everything in the restaurant is white or beige, a canvas for the food, which is meant to be decoration. Dishes are artistically arranged, as in the shrimp maltaise(pictured). The menu is eclectric, from Chili Elizabeth Taylor to turkey breast with port, cognac, truffles and duxelles to sweet-breads with shrimp and cold beef with pesto. The cafe grinds its own coffee, makes everything but the bread. Service is casual.;Picture 11, Morgan's - Having changed ownership from Jay Guben to Restaurant School graduates, it is a very fashionable restaurant in an unfashionable location. A Mediterranean bistro with wine racks as decoration and classical music, Morgan's uses fresh herbs, pine nuts, pistachios and filo dough wherever possible, and glories in its dessert display of professional-looking gateaux and tortes decorated with fruits and flowers. Occasional culinary spectacles include fresh truffles, snow pea sorbet and caviar barquettes.;Picture 12, Vincenzo's-Owned by Jay Guben, this neighborhood Italian restaurant is staffed by Restaurant School graduates, a new crew each year. The staff proudly call it the ugliest restaurant in the whole world, and boast, too, of their pasta primavera(pictured) and crespelle Belvedere, a cold layered crepe concoction with meats, tuna, vegetables, fontina cheese, homemade mayonnaise, sour cream and caviar. Pine nuts are found in the fish(with capers)and game hen(with grape leaves).;Picture 13, Knave of Hearts-South Street restaurant with theme of decadence. Other South Street restaurant includeLa Terrasse, started over a decade ago as an alley cafe and now a small French terrace restaurant, The Spanghetti Factory, La Fondue,Grendel's Lair, Philadeli,Jim's Steaks, Famous Delicateseen, South Street Creamery, JC Dobbs, Sweet Things, East Philly Cafe, Downey's, Stairs and Ship.