LaGuardia High School is squandering its legacy of artistic glory, critics say — and kids are voting with their feet.

Over the last decade, applications to the world-famous “Fame school” plummeted by 73 percent, from more than 15,000 in 2012 to less than 5,000 in 2019 and 2020, as competition for seats in other top-ranked high schools held steady.

LaGuardia’s enrollment dropped by 19% between 2019 and 2021 — the only one of the city’s nine elite specialized high schools to lose students during the pandemic shutdown. The decline triggered a $1.25 million cash infusion from the Department of Education to paper over a yawning budget gap.

At the same time, the school’s star-making machinery, which cranked out hundreds of renowned actors, musicians and artists for more than 80 years, seems to have ground to a halt.

As recently as 2015 — when Jharrel Jerome snagged a starring role in an Academy Award-winning Best Picture, “Moonlight,” within months of his graduation — LaGuardia students frequently rocketed into showbiz straight from its storied halls.

Ansel Elgort starred opposite Shailene Woodley in “The Fault in Our Stars” two years after his 2012 graduation. Timothee Chalamet of the Class of ’13 launched his career with the TV series “Homeland” while still attending LaGuardia, then scored an Oscar nomination for 2017’s “Call Me By Your Name.” Staten Island songbird Julia Gargano, LaGuardia ‘16, was an “American Idol” finalist in 2020.

But “not a single person from the classes that came after us has reached that kind of success,” said Mymoena Davids, a LaGuardia alum who graduated with Gargano in 2016.

A toxic brew of internal conflict, extreme policy shifts under two principals with polar-opposite plans, a snobbish refusal to recruit fresh talent, and even the rise of TikTok has battered LaGuardia’s prestige, insiders say.

“We are witnessing the decline of greatness,” said Frances Kweller, a private high school counselor whose clients have been balking at applying.

“It’s really upsetting to think that students could be turning away from LaGuardia,” Gargano told The Post. “That school singlehandedly changed my life. It’s irreplaceable.”

Since its 1936 founding as the city’s first public high school for artistically gifted students, Fiorello H. LaGuardia High School Of Music & Art and Performing Arts has educated generations of top actors, dancers, singers, musicians and visual artists — from Liza Minnelli, Eartha Kitt and Robert De Niro to Jennifer Aniston, Adrien Brody and Nicki Minaj.

Al Pacino, Ben Vereen, Suzanne Vega, Awkwafina, Dom DeLuise, Billy Dee Williams and Sarah Michelle Gellar are just a few of the 500-plus bold-faced names that appear on the school’s list of notable alumni.

The high-energy creative hothouse inspired the 1980 movie “Fame,” starring Debbie Allen and Anne Meara, as well as a 2009 remake featuring Kelsey Grammer. The film franchise, which spun off a six-season TV series and a Broadway musical, kept LaGuardia in the public eye for decades.

The movie’s unforgettable theme song, performed by onetime LaGuardia student Irene Cara, won the Academy Award for Best Original Song in 1980 and remains the high school’s anthem. Callers to its main office will hear Cara warbling “I’m gonna live forever!” while they wait on hold.

LaGuardia is the only one of New York City’s nine specialized high schools that doesn’t use the SHSAT entrance exam to determine admission. Under state law, candidates must pass an audition and show satisfactory middle-school grades.

That same law requires LaGuardia to provide both college-prep academics and conservatory-level arts training.

“I applied because of that dual mission, the equal focus on both academics and the arts,” said senior class president Leo Glasgow, an accomplished clarinetist who will double major in political science and Mandarin at Cornell University this fall. “LaGuardia isn’t LaGuardia because of leniency.”

But balancing those two imperatives has been a thorny problem for two successive principals — and has roiled LaGuardia’s students, parents and faculty for years.

In 2013, new principal Lisa Mars made sweeping changes to LaGuardia’s arts offerings when she arrived from the academic powerhouse Townsend Harris High School in Queens. Mars eliminated long-established music groups, including a flute ensemble, two symphony orchestras, and a symphonic band. She cut piano and guitar classes and yanked courses on orchestration and jazz.

In their place, Mars pumped up LaGuardia’s college-level Advanced Placement courses.

Many students protested the abrupt shift. “We are forced into [AP] courses we don’t want to take so that the school can boast high [college] enrollment statistics,” one group griped in an angry letter to the administration.

Davids and Gargano, sophomores when Mars took the helm, were among the first to feel the impact.

“LaGuardia was always an academically driven school. We always took AP classes,” Davids said. “But when Lisa Mars became principal, it became a matter of not one AP class a semester, but three.”

The strain on a school full of high-achieving artists — who routinely remain in the building until 10 p.m. to rehearse major productions like the annual opera — was acute.

“It was such a heavy load to pile on us,” Gargano recalled. “We were so stressed out. A lot of us just didn’t have the bandwidth.”

Meanwhile, a 2014 lawsuit revealed that Mars had overhauled LaGuardia’s admission standards to favor book smarts over talent, making the audition worth just 14 percent of an applicant’s overall score.

Nearly one-fifth of the dance students accepted in 2014 reportedly flunked their dance trials — but high grades and good standardized test scores got them admitted. That same year, an eighth-grade dancer who notched a perfect 100 on her audition was rejected for her weak junior-high transcript.

“I know kids with tremendous talent who would not have made it in under the academic criteria that principal put in place,” said Jeanne McManus, Gargano’s mother. “That’s when people started steering away.

“LaGuardia was a beautiful safe haven for kids who may struggle academically but thrive musically,” McManus added. “It was a shame to see it change.”

The Department of Education did not comment by deadline. Mars did not return a call for comment.

A dearth of arts education in city schools is also draining the talent pool, said longtime LaGuardia music teacher Paula Washington.

“Few public schools are preparing kids for the arts the way they used to,” “Washington, who retired in 2020, said. “When every intermediate school had a band, a chorus, and an orchestra, kids got their training in their schools. We’d have many applicants whose parents did not have the means for private lessons. More and more, that’s been neglected.”

The rise of social media is taking a toll too, Davids said.

“Today, everyone can be their own agent,” she said. “If you can get noticed on TikTok, or get cast from a platform like Backstage.com, honing your craft at a performing arts school doesn’t give you the leg up it once did.”

Leo and other current students cast blame on DOE incompetence. Junior-high guidance counselors in most city schools, they say, fail to point budding performers toward the school that was created just for them.

“In my middle school, I received nothing but a 10-minute assembly on how to fill out the high school application,” Leo said. “I’m only here because I did the research for myself.”

Leo is one of just two seniors who came to LaGuardia from Russell Sage JHS in Forest Hills, Queens. Meanwhile, he said, feeder schools like MS 51 in Park Slope and MS 243 on the Upper West Side usher 30 or more kids into LaGuardia each year.

“My middle school had multiple talented musicians who were also strong students,” he said. “But no one helped them. No one encouraged them to apply.”

Moreover, LaGuardia administrators reportedly make little effort to woo prospective students.

“They are completely unwelcoming,” said a Manhattan mother who recently researched high schools with her eighth-grade daughter. “There was no way to visit, and if you go on the website, there’s nothing there. It’s like they’re saying, ‘Please don’t apply.’”

In 2020, LaGuardia students launched an initiative called Outreach to assist promising kids from low-income neighborhoods — doing the work that the DOE has ignored.

“We set up Zoom calls with kids from schools in the outer boroughs,” Leo said. “We were amazed at the questions we were getting: ‘Does LaGuardia have dorms?’ ‘How much is tuition?’ They have no idea.”

“It’s completely student-run, no one in the administration participates,” he said. “But why is it that my school isn’t reaching out to these students?”

“I got the sense they’re just resting on their laurels,” said a Brooklyn dad whose daughter, a talented visual artist, was one of at least 43 members of the current junior class to flee LaGuardia over the last two years. “I feel responsible for encouraging her to think that this school was the best choice, just because of its great reputation.”

In the fall of 2018 – unbeknownst even to faculty members, insiders said – applications dipped to their lowest ebb, with just 4,263 students auditioning for LaGuardia’s class of 2023. A few months later, in June 2019, Mars was booted from her post.

Her replacement, Yeou-Jey Vasconcelos, arrived with plenty of arts cred as the former principal of Talent Unlimited, a popular Manhattan high school with a music, drama and dance focus.

Vasconcelos soon sparked her own controversy when she tried to reverse Mars’ policies. In 2021, some LaGuardia parents protested when the new principal proposed a cutback on AP classes – in part because “standardized test scores reflect systemic racism rather than student achievement,” families were told.

Applications rose to 9,776 as Vasconcelos notched her first full year as principal — and as auditions were submitted virtually due to COVID-19.

But last month, anger erupted again when students nearing the end of their AP Calculus course learned that the class had been deemed ineligible for AP credit. Two weeks later, after media outcry, the course regained its AP certification, but the damage was done.

“It looked like the administration was sabotaging the kids who have a more academic focus,” said a parent leader. “All the families who were pushing for more AP classes last year have students in that calculus class.

“Everyone says they want to achieve that dual mission,” the source said. “But it’s very difficult with an administration that’s so heavy-handed and, apparently, retaliatory.”

Vasconcelos declined to comment.

Gargano says the mission must be rescued.

“I would not be where I am in this industry without my LaGuardia experience,” she said. “When you know that every person in the building has been accepted because of their skills and their smarts, it does so much for your craft. You never find that level of talent out in the world.

“It’s just the coolest place in the universe.”