The youngest Zappa act on tour.

I never thought I'd see a 17-year-old girl sing "Keep it Greasy," or that it would be a curiously sweet thing to behold. But that's exactly what happened when Lauren Polly belted out her rendition of one of Frank Zappa's filthier tunes as part of the Paul Green School of Rock Music's tribute to the late guitarist and composer at Northsix this past Saturday afternoon.

The show was a fundraiser for the New York Underground Film Festival, and was also the Big Apple debut for these budding rockers from Philadelphia. With an audience of fellow students cheering her on, and supportive parents capturing the whole event on home video cameras, the atmosphere was closer to that of a high-school swim meet than a rock concert. The teenage earnestness of it all was endearing, and, more importantly, Lauren's faithful rendering of Zappa's utterly dirty lyrics was perfect both in technique and in the attitudinal flavoring that Uncle Frank used to call "eyebrows."

The repertoire ran from straightforward rock tunes like "Tell Me You Love Me" and "Magic Fingers" to intricate instrumentals like "Uncle Meat" and "Peaches en Regalia," and the arrangements betrayed an obsessive love of Zappa's chronologically schizophrenic live retrospective, You Can't Do That on Stage Anymore. The young musicians, ranging in age from 12 to 18, were so good that it was often difficult to remember that they were just kids. Before the show, they engaged in standard high-school behavior like wolfing down pizza and dragging one another off to far corners to whisper dire secrets. But onstage, they possessed the kind of sophistication that can only come from performing regularly in front of a crowd, with nothing but your chops to rest on.

Playing out is an important part of the curriculum at the Paul Green School of Rock Music. According to its website, "before long we have our students playing shows. Not your old fashioned wait through fifty other kids mangling their songs until your kid's turn arrives, but real rock concerts?at real rock venues, complete with light shows, and (when appropriate) smoke machines."

The school's seeds were planted in 1997, when Paul Green started teaching guitar full time. Within a year, his students were jamming together at his band's practice space, and by 1998, a group of 18 future rockers began playing at art openings and hip venues in Philly. Since then, they've been filling rooms whenever they play at home, thanks to enthusiastic local coverage, an AP write-up and an article in the May 2002 issue of Spin, written by ex-Smashing Pumpkin James Iha. In 2000, the school moved into its own space, which has since expanded to 2400 square feet and includes a repair shop and small, student-run recording studio. Don Argott, an independent filmmaker, is working on a documentary about the school, which may be parsed down into a reality show for VH1. "We got a meeting," Green told me before the show, and he beamed at the thought of the possibilities.

The kids' accomplishments can be attributed in part to Green's belief in classic rock fundamentals. "I don't want to create a legion of cover bands," Green insisted, "but I feel there's a really important second step that's been missed. Jimmy Page played in shitty bar bands before he was in the Yardbirds. Nowadays, kids get signed out of the garage, and once their initial creativity and genius runs dry, they have no foundation to fall back on." It's a lot like high-school bands, but in this case, that foundation is more Bonham than Sousa.

Though the students play shows dedicated to Black Sabbath and Led Zeppelin, among others, their Zappa tribute attracts the curious more than any other.

"Kids playing Zeppelin is cute," Green explained. "Kids playing Zappa is intriguing."

Do the kids dig Zappa's obtuse and rhythmically difficult tunes?

"If they don't start out as Zappa fans, they end up as them."

The kids concur, according to percussionist and singer Eric Slick, who's been playing with the school since 1998.

"Zappa's different from shows like Pink Floyd or Zeppelin, who took themselves so seriously. There's a fun factor involved. A lot of nights, we can barely play because we're laughing so hard."

Earlier this year, the students got a chance to play with the Project/Object, a Zappa tribute band featuring a few of his former sidemen. Napoleon Murphy Brock, sax player and acrobatic lead singer with some of the funkier incarnations of the Mothers in the early 1970s, was duly impressed and sent autographed pictures to all the kids. Thanks in part to Brock's cheerleading, the School of Rock will travel to Germany later this summer to play in "Zappanale," an annual celebration of all things Frank.

Green recently received a call from Gail Zappa, Frank's widow. Though she is known for issuing "cease and desist" orders to Zappa recreationists, she apparently gave the school her tacit approval, as long as they steered clear of a few heavy guitar workouts whose live performances were willed to son Dweezil. (During the sound check, when a student started to chime out the opening arpeggio of one verboten tune, "Zoot Allures," Green waved his hands frantically. The guitarist quickly switched over to Zep's "Bring it on Home.")

Green corralled and conducted the kids with a demeanor somewhere between a football coach and a cool older brother who will lend you his copy of Trout Mask Replica. When the kids played, he restricted his leadership to organizing onstage blocking and the shuffling of musicians. He even engaged in a bit of Zappa-esque guided improvisation, using hand signals to create a spontaneous bit of musical tomfoolery replete with classical quotations and goofy lyrics.

One very cool aspect of the school's show, and of the school itself, is a strong female presence. There are many more girls in the school than one might expect, and they sing lead vocals on many of Zappa's throatier songs like "Zomby Woof," belted out by guitarist Madeline Diaz-Svalgard. Amy Liebman, a guitar student, says gender is no problem at all. "We try not to make it an issue," she said. "Most of the girls have been in the school just as long as the guys, so they're just as good." Amy said she used to be in the Zappa extravaganza, "but I'm not anymore, 'cause I suck."

Friends nearby reassured Amy that she didn't suck, but lack of self-confidence is a problem for any teenager, even students of rock. While all the kids had more than enough chops, some of the singers looked slightly embarrassed to be onstage (though as Zappa himself pointed out in his autobiography, it's hard not to feel silly when singing lyrics like "Andy Devine had a thong rind"). More than once, I saw Green signal his charges to make eye contact with the audience, which a few were reluctant to do. "There are kids who think they suck who are awesome, and kids who think they're awesome who suck," Green told me. "My job is to balance it out."

The highlight of the afternoon (other than the sweetly perverse "Greasy") was the rendition of "Montana," in which singers Diaz-Svalgard and Teddi Tarnoff nailed a ridiculous vocal run with enormous range and insane rhythmic complexity. The crowd burst into applause upon completion of their feat, and the girls themselves?who had appeared a little uncomfortable minutes earlier when tackling "Pygmy Twylyte"?looked a bit shocked at what they had just done. In a year or two these kids will be able to hoist one eyebrow high, Zappa style, and be amused rather than amazed by their own talent.