'High School Musical 3: Senior Year" star Zac Efron says the third chapter of the vaunted tween-tastic Disney franchise arrives with built-in drama.

"Anyone who has been to high school knows senior year is the most exciting year," Efron says. "It's the year you've been waiting for.

"It's your transition into your adulthood. It can be scary, it can be exciting. Most of all, though, it's confusing. You don't know what you want to do with your life or where you're going."

No doubt the cast members of "HSM" (it's all about the acronyms) can relate. Two years ago, they were all unknowns. Now, after the first two Disney Channel movies sold more than 15 million DVDs and 13 million soundtracks, the ensemble is making the leap to movie theaters for a grand finale. (Though, high schools have reunions, don't they?)

From there, who knows? Efron just got back from Toronto, where he was helping promote a lead turn in Richard Linklater's indie charmer, "Me and Orson Welles." He signed on for "Senior Year" only after making sure the Wildcats would graduate with style. (A $3 million payday didn't hurt, either.)

"The first two movies were fun, and I didn't just want to do a third one to do a third one," Efron says. "It feels like the fans demanded it, so we should deliver. We had to end this Wildcat legacy. And by now, we've learned what works and what doesn't a lot better."

To that end, Efron says everyone (mom and dad chaperones, included) will dig the 10 new songs in "Senior Year" as well as the ramped-up production values. The story will cover all the expected senior-year milestones -- prom, graduation, a spring musical -- but Efron knows it's the songs that make or break the show.

"It's funny because I complain about singing them every day for a month while we film the movie," Efron says. "Then a mom will come up to me and say, 'Are you kidding me? One month, you had to sing them? We listened to them all year.' With that kind of repeat play, you've got to make them good."