A chain-reaction crash involving a school bus snarled traffic on the Sprain Brook Parkway in Hawthorne Thursday. Police say the school bus was carrying seven mentally handicapped students ranging in age from 6 to 15. The students were shaken up and taken to the hospital, but there were no serious injuries.One of the people involved in the three-vehicle accident says roadwork and a closed lane triggered the crash around 3 p.m. A couple in a car that hit the bus was also sent to the hospital, but their injuries were not severe.