If you produce a television movie with the humble title

High School Musical

and, lo and behold, the show turns out to be a monster hit, it makes sense to transform the movie into a musical for high schools.

And community centers. And camps. And middle schools (especially middle schools, where everyone wants to be in high school).

And on professional stages in 60 cities, including Philadelphia. Tonight, as any area 11-year-old girl can tell you, Disney's High School Musical - that's the official name of the stage production - opens at the Academy of Music for 16 shows through July 22, the second stop on the national tour.

Produce a television sequel? Absolutely - High School Musical 2, which, any 11-year-old girl can also tell you, premieres Aug. 17 at 8 p.m. on the Disney Channel.

A feature movie release? Obviously - High School Musical 3, scheduled for theaters sometime next year.

Put it on ice? High School Musical: The Ice Tour begins Aug. 31 in Florida, arriving in Philadelphia Dec. 28 at the Wachovia Center.

A book? High School Musical: The Novel sold 1.2 million copies.

Video games? HSM: Sing It for PlayStation 2 and Nintendo Wii, and HSM: Makin' the Cut for Nintendo DS, all coming next month.

High School Musical is the Grease of the 21st century.

Except Grease instructs good girls to go bad and break rules and, at least in the movie, smoke cigarettes - perhaps not the best lessons for children - while HSM is about being true to yourself while embracing new challenges and not being boxed into stereotypes and, as the song says - the song where the entire audience goes crazy in the theater - "We're All in This Together."

Since debuting Jan. 20, 2006, HSM has become huge business for Disney, a company that knows a thing or two about synergy and brand extension. The television special alone has been seen by 170 million viewers worldwide.

The CD has sold 7 million copies and was the top-selling (quadruple platinum!) album in 2006. The DVD has sold 7.8 million. The 42-date national concert arena tour, which began in November 2006 and came to the Wachovia Center Jan. 11, sold out. Everywhere.

And then it went to South America, attracting 100,000 fans in Buenos Aires.

"A month or two before the television movie aired, we took a look at the show and thought, 'Maybe we want to get this into the schools,' " recalls Steve Fickinger, Disney's vice president for theatrical licensing and one of the Magic Kingdom's happier men these days. "And then it became a huge sensation and we all looked clever and impressive."

Normally, in the first year Disney offers a vehicle for theatrical productions, "you're lucky to have around 500 school and amateur groups," Fickinger says. "In the first eight to nine months, we've granted 1,500 amateur licenses and had 15,000 inquiries."

Licenses begin at $500 for a few performances before a small group, such as a camp, and climb from there based on theater size and production run. The projection is for 2,000 amateur productions in the first year. Most likely, you know someone who's been in one.

"One of the things we've found is that, in all the schools, they've had a record number of kids coming out for auditions, kids that might have never tried out before," Fickinger says. "It's a case of art imitating life which is imitating art. The story gives you permission to try something new."

Disney has granted six professional HSM dramatic licenses. The national tour originated with Atlanta's Theater of the Stars production.

Fickinger has been with Disney for 13 years. "The last time it felt like this was The Lion King 10 years ago. People couldn't see it enough, either."

HSM is the story - oh, who are we kidding? - it's about a high school musical.

Staged at fictional East High in Albuquerque, the musical within the musical stars two unlikely tryouts, a science scholar and a star of the Wildcats basketball team, who win the leads and each other's hearts.

In the musical their names are Gabriella Montez and Troy Bolton, but in the tween world they are forever known as Vanessa Anne Hudgens and Zac (Does he really need a last name?) Efron, who starred in the television movie and its sequel.

Allegedly, they're a couple in real life, according to every one of the planet's tween magazines, which seem required by law to have Zac on the cover. Vanessa and Zac are the Liz and Dick of the tween set without the breakups and the jewelry. Or the Angelina and Brad, without the United Nations of babies and unfortunate Jen stuff. (Zac is also in Hairspray, the movie, which opens July 20 and is the reason he was the only lead not to make the concert tour.)

The other major roles - Sharpay (don't ask) and Ryan, Chad and Taylor - have made huge stars of Ashley Tisdale, Lucas Grabeel, Monique Coleman and Corbin Bleu.

The absence of these dazzling players from the new touring company, which features slightly older Broadway vets, should not diminish the stage production's appeal. Young girls, who constitute HSM's biggest fans, adore the story, the characters and the songs, committing every detail to their tender hearts. Disney's betting they'll be happy, even without Zac.

At the end of every show, the audience is treated to a megamix - standard in many musicals since Mamma Mia - a six-minute medley and sing-along that means, as Fickinger says, "all the little moppets can dance in the aisle and have a party."

Then, afterward, they can adjourn to buy HSM apparel in the lobby - this is Disney, after all. As Fickinger says, "you haven't lived until you see a little boy in a Troy Bolton jersey down to his knees."

Contact staff writer Karen Heller at 215-854-2586 or kheller@phillynews.com.