"Grease," which opened at McKeesport Little Theatre Friday, is a musical all about the anxiety, awkwardness and energy of being a teenager.

On stage and film, though, the students of 1959 Rydell High have usually been portrayed by polished older professionals. Both Olivia Newton-John and Stockard Channing were in their 30s when they played Sandy and Rizzo in the 1978 film.

Of course, there are reasons why older performers usually play teens -- they have the experience and technical ability to put on a seamless show. But those slick performances can lack the unpredictable chemistry that real teens and young adults provide. As this production of "Grease" proves, sometimes what you lose in polish, you get back in energy and authenticity.

Ryan Baker, Erik Flores, Brendan Conoway and Jeff Burgess play Danny Zuko's buddies Doody, Roger, Kenickie and Sonny. Their lewd clowning, both as a gang and with the Pink Ladies, supplied much of the show's humor and energy.

Both Mr. Conoway and Mr. Flores displayed a gift for physical comedy. Mr. Conoway twisted himself like a pretzel to wring out the laughs in his role, and Mr. Flores was winning in his scenes with the ever-snacking Pink Lady Jan, played by Amanda DiGregory.

Pink Ladies Frenchy, Marty and Rizzo, played by Sara Fischer, Felicia Freger and Stephanie Humes, also meshed well. Ms. Fischer's Frenchy was charmingly bubble-headed, and Ms. Humes gave us a hard-as-nails Rizzo while hinting at her vulnerable side.

Hannah Jo Weisberg, who plays Sandy, is only 14, but she confidently took the role in a new direction that capitalized on her obvious comedic talent. Ms. Weisberg is well-matched with Erik Barvinchak as Danny, since both display such self-assurance on stage.

Director Dan Kirk has drawn fine performances from his young cast, even if scene changes sometimes slowed the pace.

But in a surprising turn for a musical, the acting was superior to the singing. Ms. Weisberg and Mr. Barvinchak had some lovely moments in "Summer Nights" and Mr. Barvinchak's "Alone at a Drive-in Movie" was a high note, along with Jason Wisniewski's "Beauty School Dropout" as the Teen Angel.

But Ms. Weisberg too often sounds like she's belting "Tomorrow" from "Annie" when the music calls for something sweeter. Likewise, Rizzo's multilayered number "There are Worse Things I Could Do" demands careful musical interpretation, but Ms. Humes just looked vaguely unhappy throughout.

In short, this "Grease" is sometimes awkward and uneven in spots, but full of energy and conviction -- just like real teenagers.

"Grease" continues at McKeesport Little Theatre tomorrow, Saturday, Sunday and Sept. 28, 29, and 30. Call 412-673-1100 for tickets.