During a fire drill Tuesday, new University High School Principal Daryl Hart swept through the halls of the building like he'd been doing it for years. He knows many of the faces of his 1,800 students with the same familiarity. Weaving in and out of a sea of bodies, Hart does his best to remember as many names as he can, and he doesn't mind if the students shout the nickname they created for him. "It was between 'Big D' and 'Heavy D,' " said Kellen Lewis, the school's student body president. But neither of those seemed like the right fit. "So he let us call him D.H. He's pretty cool."