Bob Verini

LOS ANGELES — Back in 1960, Paul Lynde gave voice to the parental anthem of all time in “Bye Bye Birdie” when he barked out Lee Adams’ immortal lyric: “Kids!/I don’t know what’s wrong with these kids today!”

Half a century later, the musical theater is still trying to figure out what’s wrong, or at least what’s up, with kids today — raking in coin and garnering praise in the bargain.

Broadway’s hard-rocking “Spring Awakening” sees sexual repressiveness as the source of youthful woes in a 19th century German high school, while in a Northern English mining town in the forthcoming London import “Billy Elliot,” the conflict can be traced to economic hardship.

The new stage adaptation of telepic smash “High School Musical” recommends healing the good old Mickey and Judy way — by putting on a show, while in the perennially popular “Grease,” due for Broadway revival this summer, true love is the answer for the students at Rydell High.

But “13,” which opened Jan. 7 at Los Angeles’ Mark Taper Forum, is a special case because it’s all kids, all the time. There’s only one actor over 15, lead Ricky Ashley, and even the band is underage.

Composer-lyricist Jason Robert Brown, working with juvenile novelist Dan Elish, was determined that “it never feel like a show written by a bunch of old guys putting their thoughts into the mouths of teenagers.”

“You just let them do it,” adds director Todd Graff. “You get out of their way.”

Here’s Brown’s answer to Lynde, as a lonely teenager explains why it’s better to shut yourself off with shades and attitude:

“When you’re cool you don’t care if people disappear/You don’t care if your dad’s not here/You don’t care if your life’s been uprooted and bent/Without your consent/ A geek’s afraid it’s never gonna be OK/But the cool kid knows it doesn’t matter anyway.”

“There’s something universal there — we’ve all felt like the outsider,” says Center Theater Group artistic director Michael Ritchie, who commissioned a 2006 workshop of “13” from a demo CD of four songs.

In rehearsal, the cast proved invaluable in keeping the creators honest and true. One day Brown suggested that a character, asked how things were, should reply: “Right now it feels like ass.”

Says Elish, “I was actually embarrassed by that. What does that mean? Nobody would ever say that. And then Ricky said, ‘You know what new line I really love? “It feels like ass!” That’s exactly what a kid would say!’ ”

Producers have long balked at large-cast kids’ shows because of disciplinary problems. “I made a decision from the jump to treat them like pros and expect them to rise to the occasion,” says Graff, who worked with teen talent before on his indie movie “Camp.”

“As long as you’re straight and clear with them, and set a bar that’s reasonably high, they feel they’re being taken seriously and they work like Trojans,” he adds.

When they let him down, Graff says, “it was just about being unable to stay focused and shut up. So once a week we’d have The Talk, about professionalism and this being high-stakes show biz, and that it’s more important that the audience have fun than we do.”

“13” could catch on with its peer group and parents alike, and give Brown the breakout hit everyone’s been expecting since his 1999 Tony for “Parade.”

While CTG has successfully shepherded “The Drowsy Chaperone” to Broadway and will follow this season with its Rialto transfer of “Curtains,” Ritchie says it’s too soon to decide whether “13” will be Gotham-bound.

“Still, you’d be hard pressed to hear the cheering every night and not believe there’s a reason to produce this show now,” he says. “We’re a theater for everybody, and it’s part of our constant effort to bring in a new subset of people.”

Graff explains the appeal simply: “Kids like to see themselves.”

Could there be a whole new generation of dazzled kids, who will respond to seeing their lives reflected onstage by morphing into regular theatergoers? And, maybe become inspired to put on their own shows?

Now, that certainly would not feel like ass.