SPRING HILL — A 63-year-old Spring Hill man was seriously injured Monday when his Ford Mustang crashed head-on with a school bus, authorities said. Michael Lee McCall was driving west on Elgin Boulevard about 2:20 p.m. when he failed to negotiate a curve in the road, causing the Mustang to cross into the eastbound lane and collide with a Hernando County School District bus, the Florida Highway Patrol said. There were no children on the bus. McCall was taken by helicopter to Regional Medical Center Bayonet Point in Hudson. The bus driver, 62-year-old Thomas Kehoe of Spring Hill, was treated for minor injuries at Oak Hill Hospital in Spring Hill. An adult passenger on the bus was not injured. Troopers said the crash remained under investigation Monday and charges were pending.