Teachers, students and an impressive array of graduates reflect on the mystique and challenges of Juilliard, the prestigious performing-arts school that's part of New York's Lincoln Center. Director Maro Chermayeff (PBS's “Frontier House”) follows four current students (a dancer, an actor, a pianist and a singer), but driving the program is the commentary of some 50 alums (and others, like Eriq La Salle, who didn't make it through). Among them: Itzhak Perlman, Kevin Spacey, Audra McDonald, Emmanuel Ax, Wynton Marsalis, James Levine, Bradley Whitford, Kelsey Grammer, Marvin Hamlisch and Robin Williams.