A procession of teenagers with hard-faced stares strutted through an evening rain during a small fashion show in Lower Manhattan, causing a mixture of delight and bewilderment among passers-by who witnessed the spectacle.

As techno music blasted, one teenager after another stopped to pose for cameras in a cordoned-off area of Gansevoort Plaza in the meatpacking district. Upon their return to a tented area, they exchanged hugs and high fives with their fellow models. Couples having dinner at Serafina and chic women on their way to Pastis did double takes.

After all, wasn’t New York Fashion Week not until September? And why was the audience cheering with the kind of abandon typical of parents at a graduation ceremony?

As it happened, the event that took place last Wednesday evening was a graduation ceremony of sorts: This was the annual runway show for the senior class of the High School of Fashion Industries, the only trade-based public school in New York City dedicated to fashion.

The school was founded as a vocational institution in the 1920s and occupies an old Art Deco-style building in Chelsea‌, and its students prepared for the evening, the highlight of the school year, with the same level of intensity that goes into producing the Marc Jacobs fashion week closing show.

Tyrone and Marlene Jackson had come to the show from the Jamaica neighborhood of Queens to support their daughter, Mia, a senior who plans to attend the Fashion Institute of Technology.

“We knew she was talented the moment she started drawing on the couch at 3 years old,” Ms. Jackson said. “Fashion Industries has prepared her for what’s next.”

“People only hear about LaGuardia,” she continued, referring to the Fiorello H. LaGuardia High School of Music & Art and Performing Arts, “but this school is the best-kept secret in New York. The kids show their gifts at this show.”

An annual tradition dating to the 1940s, the event is the High School of Fashion Industries’s equivalent to a homecoming football game. It is intended as a showcase for the looks created by seniors in the school’s fashion design program. This year’s theme, “The Elemental Ball,” encouraged designs that evoke nature.

Nearly everyone at the school chips in: Freshmen volunteer as models, sophomores work as makeup assistants and juniors serve as runway photographers. The school even offers a modeling workshop to teach students how to bring ferocity to their runway moves.

The stakes felt higher this year. Until this spring, the show had always taken place on a runway in the school’s auditorium. Now the students were showing off their creations in public — in a trendy neighborhood with strong ties to the fashion community, no less — through a partnership with the local Business Improvement District association.

These were the same cobblestones that Carrie Bradshaw once clomped across during her early morning walks back home from clubbing. And this was the site of last year’s Vogue World, a fashion extravaganza presided over by Anna Wintour that drew some of the biggest names in fashion (Balenciaga, Dior, Gucci) and its most dedicated followers and ambassadors (Serena Williams, Gigi Hadid, Lil Nas X).

For the High School of Fashion Industries seniors, the Vogue World connection loomed large. For those taking part, the chance to showcase their garments at the same site as the Vogue event brought with it a sense of fantasy and affirmation. Just before the students hit the runway, Aiamdra Estrella, who plans to attend Queens College, reflected on the moment.

“This is the first time we’ve done it like this,” said Ms. Estrella, who wore a long turquoise ruffle skirt that suggested the tropical ocean. “Tonight we get to follow in the footsteps of Vogue. We get to show the world who we are.”

Caroline Castro, who lives in the Woodside neighborhood of Queens, wore a green floral dress that she had designed from sustainable elements such as rose stems, bottle caps and coffee filters.

“When we learned the show would be where Vogue World happened, we knew how important this was,” she said. “We need more eyes on our school. We need better funding. Lots of New Yorkers don’t know about us. Some of our sewing machines barely work.”

“This dress is for my mother,” she added. “She came from Colombia and became a babysitter for families on the Upper West Side. I’m going to Parsons next year and I’m dreaming big, because she gave me everything and I want to give back.”

‘Where’s the Sass?’

Early in the morning on the day before the show, at the school’s labyrinthine building on West 24th Street, nervous energy coursed through the fluorescent-lit hallways as students hurried through their final preparations.

In a studio filled with mannequins and old Singer sewing machines, Anyah Lewis, a senior, finessed a set of plastic moth wings. Beside a row of lockers plastered with fliers promoting the show, Jacob Santiago, a freshman, practiced his strut. And on a red brick balcony aglow with sunshine reflecting off the Empire State Building, a rehearsal was taking place.

Seniors lined up along the balcony, some of them yawning as they woke up from their morning commutes, from Mott Haven, Harlem, and East New York. But as soon as Britney Spears’s “Gimme More” began playing from a portable speaker, they snapped into action, maintaining hard stares as they vogued down a practice path outlined with tape.

Brenda Rojas, a teacher nicknamed “the runway drill sergeant,” barked feedback at them. Some 30 years earlier, Ms. Rojas had modeled in the show as a student at the High School of Fashion Industries.

“Give me some animal,” she told a weary-looking teenager.

The student placed a hand on her hip.

“That’s better,” Ms. Rojas said. “Strike that pose. Eat it.”

Another student model appeared on her runway.

“Where’s the sass?” Ms. Rojas said. “I don’t see any sass!”

The drill came to an end 15 minutes later. After the faculty members huddled to deliberate, one of them bellowed, “OK, let’s run it again.” And the students got back into formation.

Almost a century ago, the High School of Fashion Industries was founded as the Central Needle Trades High School. It operated out of a garment loft, teaching immigrant students how to sew, tailor, drape and sketch.

After an expansion led by the Works Projects Administration, it reopened in 1940 at its current site. The auditorium contains a landmark mural painted by Ernest Fiene that illustrates the struggles of early garment workers, including a depiction of the 1911 Triangle Shirtwaist factory fire.

In the 1950s, the school changed its name to the current one, and it gradually developed a fully fledged academic curriculum. Today it has some 1,600 students and offers majors including photography, merchandising, visual display, and graphics and illustration. Among the school’s best-known recent alumni is the Haitian American designer Kerby Jean-Raymond, who founded the fashion label Pyer Moss.

“We’re like the Hogwarts of fashion,” Kate Boulamaali, an assistant principal, said in an interview at the school. “And we’ve been here a long time. This show, whether it was more atelier experience at first, then more runway later, has happened in some form here practically since the beginning.”

Ms. Boulamaali cited fashion brands that have supported the show, such as Coach and Stuart Weitzman, which donated shoes this year, and Swarovski, which provides crystals. She mentioned some of the industry figures who have visited the school, like Tommy Hilfiger and Betsey Johnson. She recalled when André Leon Talley was made principal for a day and how he offered critiques of student holiday window designs.

Ms. Boulamaali also stressed the challenges of running a school that must prepare students for careers in an industry that can be as exclusionary as it is glamorous.

“The majority of our kids come from homes that are at or below poverty level,” she said. “We’re here to make sure they know they also belong and that their financial status shouldn’t stop them. Sure, they’re going to have to work a little harder, but our kids aren’t afraid of hard work.”

“We have disabled students here, autistic students and nonverbal students,” she added. “You want to see someone with special needs who is still getting a chance to create fashion? Then come into our classrooms. We make sure everyone knows they have a shot.”

Showtime

On the morning of the show, crowds of students began their journey from the school to the meatpacking district. Moving as one teenage swarm, they pushed garment racks through the streets for about 10 blocks, to Chelsea Market, where they hunkered down in a private room to begin their backstage prep.

Empty pizza boxes piled up as they coifed one another’s hair with curling irons, applied press-on nails. Ali Rendich-Quinlan, a senior, practiced her moves in front of a mirror. Cavelin Sahba, a tall junior who volunteered to model in the show, sat with his eyes closed as Noreamy Almanzar, another senior, dabbed foundation on his face.

“I wanted to step out of my comfort zone, so I volunteered,” Mr. Sahba said. “But now I find it empowering. It’s not just a walk.”

Ms. Almanzar applied eye shadow, saying, “The designer, Jayden, wants a smoky eye, so I’m building everything out so he can look amazing up there tonight.”

As showtime approached, about 100 teenagers marched en masse to Gansevoort Plaza and formed a long line behind the runway tent. Parents, alumni, faculty and representatives of the New York City Department of Education were already seated. The sky had suddenly grown dark.

“Get ready — it’s going to rain hard,” a teacher yelled. “The show must go on!”

As if the weather wasn’t enough, it seemed to hit home, for some of the participants, that they were about to put on a fashion show at the same site the pros use. Nameera Mehdi, who wore a pink sari-like dress inspired by her Indian heritage, wasn’t intimidated by Vogue’s shadow.

“I can’t wait to walk,” she said. “We’re the future generation. They’re going to see what we’re about.”

As the line moved forward, the rain began to fall.

“Tell Vogue,” Ms. Mehdi said, “that we’re coming for them.”