A school bus was involved in a collision in Billings on Tuesday while students were on board.  The Gazette reports that at about 11:30 a.m. the bus hit a truck while turning onto Broadwater Avenue from Eighth Street West.  Billings Police Sgt. Mitch Hart said the woman driving the bus southbound on Eighth told officers she entered the intersection on a yellow light.  The man driving the truck said he had a green light when the bus pulled out in front of him.