THEATER REVIEW:

On a normal opening night visit to the Orange County Performing Arts Center, one might notice a predominance of gray hair, and no hair, in the orchestra section.

Tuesday, however, that demographic was drastically altered. In fact, you could estimate the average playgoer’s age at 10 and probably not be too far off.

The reason, of course, was “High School Musical,” the Disney-produced musical comedy that’s both family friendly and a glittering treat for the older audiences. And it’s in town only this weekend.

“High School Musical” takes three familiar undergraduate elements — the jocks, the brainiacs and the artsy crowd — and sets them at odds as two personable students set out to win the leads in the school’s new show once they take care of their basketball and science competitions, respectively.

The show is somewhat derivative — especially for those who have rocked out to “Grease” for the last 30 years. In both shows, the main characters have already met before school starts, and the ensemble number “We’re All in this Together” brings to mind the closer from “Grease” titled “We Go Together.”

Nevertheless, “High School Musical” is a great deal of fun, with an energetic ensemble generating waves of school spirit — thanks to the upbeat direction of Jeff Calhoun and the imaginative choreography of Lisa Stevens.

The leading characters — hoops wizard Troy Bolton (John Jeffrey Martin) and science sharpie Gabriella Montez (Arielle Jacobs) — hold the only chances of dethroning the drama club regents, twins Sharpay and Ryan Evans (Helene Yorke and Bobby List), who have been headlining the school musicals “since birth.”

Unfortunately, all three events — the basketball playoff, the science decathlon and the final musical tryouts — have been scheduled at the same time, which necessitates a little creative time management.

Martin and Jacobs mesh naturally together and manage to flesh out their limited-dimensional characters.

Yorke and List have plenty of dimension with which to work, and they strut it with gusto, especially Yorke, who revels in her position of adoration and virtually henpecks her younger (by a few minutes) brother.

The primary performance, however, is delivered by an adult, Ellen Harvey as the drama coach, whose dulcet tones echo through the school halls.

Ron Bohmer is strong as the basketball coach whose son (Martin) is the star player, and who is cut no slack. Michael Mahany scores as the spirited “voice of East High” on the school PA system.

Olivia Oguma underplays to the hilt as the shy music lover who has created the school’s new show — “Juliet and Romeo,” an updated (and upbeat) version of the Shakespeare tragedy in which the title characters survive.

Shakiem Evans and Jelani Remy lend strong support as Martin’s basketball buddies.

“High School Musical” has generated a huge following among teens and pre-teens, but locals have only this weekend to catch the live version at the center. It’s a romping, stomping riot of energy and acumen.

IF YOU GO

WHAT: “High School Musical”

WHERE: Orange County Performing Arts Center, 600 Town Center Drive, Costa Mesa

WHEN: Closing performances tonight and Friday at 7:30; Saturday at 2 and 7:30 p.m., Sunday at 1 and 6:30 p.m.

COST: $20-$70

CALL: (714) 556-5727

TOM TITUS reviews local theater for the Daily Pilot. His reviews appear Thursdays.