PORTLAND, Maine — What makes a great art school? The question corkscrews deeper into the stuff of life than you might think.

If the goal of an art school is to produce great art, you could simply reverse-engineer the question and ask: Where did the best artists go to school? Bingo! There are your best art schools.

But, of course, many great artists never bothered to go to art school. Or if they did, they flunked out; or else they went, only to learn what they didn’t want to be, or do. Creativity is crazy like that. It makes no sense.

So inevitably, other criteria enter in. Other values. Some can seem contradictory. Which art schools build best on tradition? Which jettison outdated conventions? (Both = good). Which establish the richest correspondences among people, ideas and art forms? Which offer the most individual freedoms? And where do the blueberries taste the best?

To answer such questions, obviously, you need to go to Maine.

Specifically, the Portland Museum of Art, and the exhibition “In the Vanguard: Haystack Mountain School of Crafts, 1950-1969.” It’s a revelatory show about a summer craft school that opened in rural Maine in 1950, broke down barriers between art and craft, established itself as a hotbed of creative experiment and is still operating.

In many ways comparable to North Carolina’s storied Black Mountain College (with which it had thickets of connections), Haystack had an outsize impact on art, craft and modernism in America. Among the better known artists who taught there in its first 20 years were Anni Albers (whose husband, Josef, taught at the Bauhaus and was the most important teacher at Black Mountain), Jack Lenor Larsen, Robert Arneson, Dale Chihuly, Toshiko Takaezu, Kay Sekimachi, Karen Karnes, David Weinrib, M.C. Richards, Trude Guermonprez, Wolf Kahn and Stan Vanderbeek .

Like Black Mountain, and the Bauhaus before it, Haystack built on a progressive philosophy grounded in nature and simplicity. Unlike Black Mountain — which ran from 1933 to 1957 — Haystack stayed open.

It did, however, move, about 10 years after it was founded, from inland Montville to a beautiful campus on the coast of Deer Isle, facing the Atlantic Ocean. Photographs of both locations suggest how much of the summer school’s activities took place outdoors. And of course, nowhere in America does outdoor living have quite the same tenor of sweet and concentrated transience as it does in Maine. That reality (founders of art schools, take note!) may account for Haystack’s success as much as anything.

The Portland show, organized by Diana Greenwold and Rachael Arauz, is the first major museum exhibition devoted to Haystack. It’s a joy to walk through. Smart, surprising combinations of ceramics, textiles, glass, jewelry, paintings and sculptures abound, reflecting not only the school’s non-hierarchical ethos of experiment, but also the shifting tenor of the times, as the 1950s gave way to the ’60s. Early pieces in the show are rooted in earthy craft traditions or varieties of impassive, stripped-back modernism. Later pieces are funky and in-your-face, political and, in some cases, wildly funny.

The curators interviewed dozens of former instructors and students, uncovering many works exchanged between artists and rarely or never exhibited. “Almost without exception,” Arauz said, “every single interview was some version of, ‘That Haystack summer was the most special thing in my whole life.’ ”

The school arose out of a soup of social idealism, cresting interest in modernism, a resurgent craft movement and an intuition — felt acutely in the aftermath of two world wars — that ways must be found to meld art with life, creativity with domesticity, making with being.

To describe the general conditions from which Haystack emerged is to make its founding sound inevitable: Of course a school like Haystack was established in Maine in the 1950s. It makes complete sense! In reality, its birth was extremely chancy.

The school’s founding director, Francis Merritt, was the replacement for an appointment that fell through at the last minute. Merritt and his wife, Priscilla, came to Haystack in 1951. Merritt stayed in charge for 27 years, providing many of the crucial ingredients for its sustained success.

Yet Haystack was in the works before the Merritts arrived. The money came from Mary Beasom Bishop, of Flint, Mich., the wife of Spencer Bishop, a banker and director of Buick. When he died of a heart attack in 1946, her interest in arts and crafts quickened.

Meanwhile in Montville, a group of local craftspeople had become interested in setting up a craft school near Haystack Mountain. Two of them, Marjorie and Edgar Sewell, met Bishop through her sister, whose daughter was engaged to the Sewells’ son. When the Sewells told Bishop about their dream of establishing a craft school, their enthusiasm caught on. Bishop’s financial gift in 1950 enabled the founding of the school on a scenic property on the slopes of Haystack Mountain.

Edgar Sewell designed the buildings, which included a long main lodge and dining hall, five cabins and two studios for pottery and graphics. The students started arriving in July 1951, just days after the Merritts had arrived from Flint with their two young sons. Priscilla taught weaving and Edgar Sewell woodworking, and there were classes in block printing and ceramics.

The school thrived from the get-go. Enrollment increased steadily.

But there was trouble in paradise. (There always is.) Eager to prevent Haystack from becoming a summer school for vacationing amateurs, the Sewells and their local Maine comrades promoted rigorous standards, with a strong emphasis on technique.

Merritt didn’t want hobbyists either. But he was a modernist, and his idea of seriousness was more experimental and open-ended. He welcomed people from different backgrounds. He liked experimenting and informality. He wanted freshness, freedom and a fertile atmosphere of ongoing, improvised problem-solving.

The founding group of Maine craftspeople, including the Sewells (whose marriage broke down in 1953), weren’t all equally sold on Merritt’s vision. Ambivalent about Haystack’s rapid success and expansion, they gradually peeled away or were squeezed out.

Merritt pushed on. By 1954, he had expanded the curriculum to include evening sessions on short-story writing and philosophy, and he cultivated debates about the art and craft divide.

Haystack, in all these ways, was ahead of its time. It was a place where rules could be broken and categories confounded. Over the course of its first decade, the offerings expanded to include classes in design, graphics, painting, enameling, architecture and experimental film. In its second decade, the school moved to its present location — a celebrated, eye-catching modernist campus designed by Edward Larrabee Barnes on a rocky slope on Deer Isle — and cast an even wider net, offering classes in glass-blowing, jewelry, performance, writing and even cooking.

“Haystack” is still going strong. It offers classes, a residency, visiting artist programs and more. Many people visit just to see its famous main building and the beauty of its natural setting.

In those first two decades, plenty of wonderful art emerged from the school. The textiles in the Portland show are especially dynamic: Going from Anni Albers’s “Play of Squares” and Mariska Karasz’s “Procession,” both from around 1955, to Ruben Eshkanian’s “Haystack,” Olga de Amaral’s “Wall Hanging 1,” and Walter Nottingham’s “Celibacy” — all from the 1960s — offers a lesson on the meshing of social history and aesthetics that you could never get from a textbook.

Churning out “great art” was not, finally, the school’s main contribution. What was created during those short, sweet summers had more to do with the very conditions of creativity. It was something more mercurial and harder to pin down but — on all the evidence presented by this show and its excellent catalogue — very, very enviable.

In the Vanguard: Haystack Mountain School of Crafts, 1950-1969 Through Sept. 8 at the Portland (Maine) Museum of Art. portlandmuseum.org.