Cheesy? Yes. Cringe? Absolutely. That’s why High School Musical is still our secret passion | Rachel Chang

Whenever I watch basketball, I come away disappointed that the players’ shoe squeaks didn’t jumpstart a choreographed dance number, just like in High School Musical. Whether it was a lunch break turning into a confession of closeted passions or a pep rally evolving into a flashmob, the 2006 Disney Channel movie proved that teen drama can always be solved through song.

Quality entertainment? Meh. The corniest of lines? Oh, for sure. But the cheesiness was the point. Its 98 minutes became a deliciously enduring slice of pop culture not despite the cringe, but because the film embraced it so wholeheartedly.

Now, 20 years later, Troy Bolton’s dribbles and Sharpay Evans’s sparkles have sashayed their way into the London spotlight as a new stage adaptation opens at the Troubadour Wembley Park theatre this week, complete with throwback stars such as McFly’s Harry Judd and the original film’s “pop-and-lock girl” Kaycee Stroh.

No one is as shocked and exuberant as I am. In August 2005, I was an editor for the US teen magazine Popstar!, and the only journalist on the first movie’s Salt Lake City set. I hung out at East High (the real school has the same name) as a fresh-faced Zac Efron and a charming Corbin Bleu taught me the Wildcats dance in the cafeteria. In the gym one day, when the weather was particularly gloomy, I watched so many takes of Get’cha Head in the Game that I eventually opted to sit outside in the rain.

This was a time when Disney Channel movies debuted every other month, so the production seemed low key. Even so, I was keenly aware that being in my late 20s then, I was maybe three times the age of the intended audience. Paired with its TV distribution, it would likely be a niche kids’ movie at best.

So when HSM premiered to 7.7m US viewers – at the time, Disney Channel’s highest-rated broadcast ever – I was stunned. Those catchy upbeat songs that I thought played on repeat only in my head started climbing the Billboard charts as the soundtrack became the No 1 album of 2006. By the end of the year, the little TV movie had notched up 100m global viewers.

Of course, High School Musical 2 was fast-tracked. In tandem, I had graduated to entertainment editor at CosmoGIRL!, and visited the more guarded set in St George, Utah, in spring 2007, where everything was bigger and more dazzling. By now, Efron and Vanessa Hudgens’s real-life romance was a source of speculation – and I caught a clue, spotting a Troy button pin on Hudgens’s bag. The film’s director, Kenny Ortega, invited me to sit in the chair next to him, and this time I knew I was watching pop history unfold before my eyes.

Expectations were shattered once again. HSM2’s US debut in August 2007 garnered a whopping 18.6m viewers, securing a Guinness world record as the most-watched US cable TV movie.

My trip back to Salt Lake City for High School Musical 3: Senior Year – now upgraded to the silver screen – was far more calculated. I was restricted to the studio where we shot Hudgens for CosmoGIRL!’s cover, and only some of the supporting cast were brought over for interviews as I sat in a nearby coffee shop. To no one’s surprise, the October 2008 US premiere marked the biggest opening for a musical film at the time, eventually raking in more than $250m globally.

While some may roll their eyes at the bubblegum trilogy, many people were devouring the sappy storylines and bopping (to the top) with the earworms – a formula that translates as perfectly on stage as it did on the screen. The franchise has previously been made into a London stage show in 2008, with a tour of the UK, but this fresh immersive rendition promises a new interactive element, along with the songs ingrained in our muscle memory, primed for live theatre. It has already played in Salford this summer, and the run was extended due to demand.

What HSM did best was blend American high-school social hierarchy with the simplest of storylines: a jock who moonlights as a theatre geek represents the most universally relatable dilemma of embracing passion despite perception. It ushered in a new era of musicals, from other Disney productions such as Camp Rock and Descendants to Glee, Hairspray, Mamma Mia and Wicked.

The brand has splashed into all areas: Hallmark ornaments, Disney park parades, licensed high-school productions, the mockumentary High School Musical: The Musical: The Series (which introduced the world to Olivia Rodrigo), and a long list of appearances on Saturday Night Live US, the most recent of which was just three weeks ago.

HSM may never be the cool kid, but it will always be the popular one. By breaking free and embracing its goody-goody reputation, it has grown into the sugary dose of innocent nostalgia that reminds us that when it comes to guilty pleasures, we’re all in this together. And if you’re not on board, get’cha head in the game.

• Rachel Chang is a journalist and author specialising in travel and pop culture. Her book Unforgettable Walks: 52 Places to Stroll Around the World is published next year