They're back: Troy and Gabriella, Sharpay and Ryan, Chad and Taylor and the rest of the East High Wildcats. And you may have no idea who they are — unless there's a preteen in your life.

Then you almost certainly know more than you want to about "High School Musical," the Disney Channel movie that launched a thousand products and made Zac Efron, Vanessa Hudgens, Ashley Tisdale and Corbin Bleu stars among the 8- to 12-year-old set.

The sequel, "High School Musical 2," premieres Aug. 17. It includes 10 new songs and energetic choreography by Kenny Ortega, whose credits include the prom scene from the movie "Pretty in Pink" and the parade in "Ferris Bueller's Day Off" (both released in 1986), as well as the first "High School Musical."

"HSM 2" opens just as school's getting out for the summer. Sharpay (Tisdale) schemes to get Troy (Efron) a job at her father's country club in hopes of stealing him away from Gabriella (Hudgens). The job comes with the promise of a college basketball scholarship, but it also requires Troy to abandon his friends.

Will Troy grab for the gold or be true to himself? You needn't be an astrophysicist to figure it out. Maybe all you need to be is someone hoping for wholesome entertainment for children living in a world where the antics of such young-adult stars as Lindsay Lohan, Paris Hilton and Britney Spears dominate the headlines.

In an interview, Tisdale, 22, described herself this way: "I don't drink and I don't smoke. I'm not a club person. I'm not a person who loves attention and the paparazzi." That was enough to warm parents' hearts — and open their wallets — after the first "High School Musical" premiered in January 2006. (Disney re-airs the original Thursday)

"HSM" reached more than 160 million viewers in 100 countries, the Disney Channel said, and the soundtrack was the best-selling U.S. CD of 2006 and has sold 4 million copies.

Whatever it is about "High School Musical" — the undeniably catchy music; its shiny, happy stars; its positive messages of empowerment or something else entirely, the movie clearly captured the tween zeitgeist.

Gary Marsh, president of entertainment for Disney Channel Worldwide, said he first recognized the blockbuster potential for the original "High School Musical" when he saw people at the channel trading DVDs of the scenes as they were being filmed.

It's hard to get predictions — publicly, anyway — about how successful "HSM 2" will be. But producers and cast members said it's better than the first and was every bit as fun to make.

"It was a blast," said Efron, 19, a blue-eyed charmer who's breaking out as one of the stars of the movie "Hairspray." "We love to have fun, and Kenny (Ortega) just fuels that fire. He brings out all the goofiness and the youth in us."

Ortega's credits span four decades, but the choreographer said he still has "an innocence" inside himself that he used to inspire the songwriting teams, screenwriter Peter Barsocchini and the cast.

If you want to see his best work in "HSM 2," Ortega suggested paying special attention to a number called "I Don't Dance," which takes place on a baseball field and features Lucas Grabeel (Ryan) and Bleu (Chad) along with a cast of high school ballplayers and dancers.

"What's at the center of the songs," Ortega said, "is a message of hope, a message of courage, a message of not giving up too much while you're going for your dreams."