AT first glance the ensemble setting up in a fifth-floor classroom at the Kaufman Center on West 67th Street in Manhattan seems like any other student group and exactly what you would expect to find in a building that houses two music schools and Merkin Concert Hall. Teenage string and brass players tune their instruments and play fragments of pieces they are working on; saxophonists see to their reeds; percussionists contribute spiritedly to the din; and a guitarist and a bassist quietly pluck figures from the scores on their music stands.

But when the conductor, Jenny Undercofler, using a pencil as a baton, leads her Face the Music ensemble through Steve Martland’s rhythmically pointed, texturally jagged “Horses of Instruction,” you realize that this is not the sort of student orchestra you may remember. It is instead an alternative-universe high school band: a new-music factory that focuses on works written in the last 50 years, with an emphasis on the new alt-classical style. Its musicians, who began studying new music before anyone had told them that it was incomprehensible or unlikable, are thrilled to play it, and their spirit has impressed composers whose music they perform.

“Writing for a kids’ group is like throwing a pass in football,” said Phil Kline, whose “Exquisite Corpses,” composed for the adult virtuosos in the Bang on a Can All-Stars, is part of Face the Music’s repertory. “You don’t want to throw it behind them, or too far in front, but so they can reach it. But here was this group working on a piece with a clarinet part written for Evan Ziporyn and a guitar part for Mark Stewart, extraordinary players, and they did a great job. There was no sense of boredom or squirming. They were totally focused and committed.”

Now in its seventh year Face the Music has 74 members, up from 8 when Ms. Undercofler started it in 2005. It began as a project of the Kaufman Center’s Special Music School, a public school for musically gifted children from kindergarten through eighth grade. (The school will add grades nine through 12 in 2013.) But the group quickly expanded to take in musicians from all over the New York region, from Grades 5 through 12 (roughly, 11 to 17 years old).