She came out of retirement to lead Furr in 2000. Back then, gangs ruled the campus. Barely half the kids graduated. Simmons thought she’d last three months. Seventeen years later, she leads a national experiment at Furr to transform the high school. Last fall, the school won a $10 million grant from the XQ Institute, a foundation led by Laurene Powell Jobs, the widow of Apple co-founder Steve Jobs.