A hum and chatter reverberates against the clean walls of a 90-year-old hallway above Oakland’s historic Fox Theatre. This is home for the Oakland School for the Arts, a charter school established in 2002. It’s Friday afternoon and the middle school students are giddy with anticipation. Two harmonious bells chime, signaling the day’s end. “We always have different bells that we play for the kids,” said executive and artistic director Donn Harris. “That’s a nice one. It’s got a kind…