TAMPA — Three Hillsborough school buses collided in a slow-speed crash Monday, sending four students to the hospital with minor injuries. It happened on a bus transfer ramp at Osborne and Central avenues, police said. One bus rear-ended another, pushing it into a third. Kids onboard were from Cahoon, Lee, Dunbar, Lockhart, Lomax, MacFarlane Park, Muller and Shore elementary schools; Orange Grove, Stewart and Williams middle schools; and Blake, Middleton, Jefferson and Tampa Bay Tech high schools. Driver Aileen Hargrove, 47, was cited for careless driving and driving with her license suspended without knowledge.