Disney's "High School Musical 2" neatly proves Spanish philosopher George Santayana's claim that those who forget the pain they experienced in high school are condemned to repeat it.

The show is an exceedingly thin and shallow sequel to its saccharine predecessor, successfully staged last year by Army Community Theatre. But while "Musical 1" scored by tapping into adolescent female romantic fantasies, "Musical 2" works its chorus very hard, but never manages to fan the same flames.

The same central characters reappear, this time at a private country club where an end-of-summer talent show pits the staff against the guests. Doesn't anybody at Disney remember that "Dirty Dancing" already cornered the market for that plot?

The ACT production is also something of a homecoming reunion.

Coco Wiel again directs, and Philip Amer Kelley graduates to doing sole choreography. Between them, they keep the young cast of more than 40 dancers and singers smiling and jumping.

Kyla Kashimoto displays a rich and mature voice as Gabriella and Seth Lilley is a somewhat tarnished heart-throb as Troy — tempted to stray by the prospect of a college scholarship.

Jana Souza gets to play bad girl Sharpay, a neat about-face from her role as good girl Gabriella in last year's show. Vincent Fitz-gerald repeats as Sharpay's brother Ryan, continuing a slow, but steady character arc that begins to make him more likeable than Troy.

That's interesting from a character development point of view, but when we start to think that Gabriella would be better off to dump Troy and hook up with Ryan, it means that something terribly wrong may be happening while East High is on summer vacation.

The biggest dilemma in this show is whether Troy will sing the special song in a duet with Gabriella — or with Sharpay. And that's not enough to power a two-hour performance.

Like the original, the music in this show is too loud, too bleating, and too unintelligible. The production is further hampered by a see-sawing sound system that doesn't find a balance until deep into the first act.

The production is also economically staged on a bare stage, with only rear projections to suggest the change of scene. The gaudy Hawaiian number is the sole, but wonderfully tasteless exception.

Jalen Thomas has a featured bit as Troy's abandoned lieutenant in "I Don't Dance," and he's good enough for us to wish he had more to do. Shah Bento carries himself well as the only adult in the show.

The ensemble's best moment comes in the finale, when interweaving choreography gives everybody in the cast a moment in the spotlight and the chorus and Daren Kimura's orchestra effortlessly pump out the wholesome energy that is a must for any successful Disney production.

Joseph T. Rozmiarek has been reviewing Hawai'i theater since 1973.