It happened at 2:40 p.m. eastbound MD 68 at Lock Tender Lane.
Police say the school bus had stopped in the roadway to release students at a pre-designed school bus stop. A 2011 Toyota pick-up truck came to stop behind the bus.
That's when a witness told police a third vehicle, a 2006 Subaru station wagon, did not stop and struck the rear end of the pick-up truck.
Police say the pickup truck was pushed forward and struck the rear of the school bus.
Two students inside the bus, ages 11 and 14, were not injured in the collision. The driver of the pick-up truck, Michael Adams, was trapped inside his vehicle and had to be extricated and was taken to Meritus Medical Center. The driver of the Subaru, Morris Fleming, was also taken to the hospital.
Both eastbound and westbound lanes of MD 68 were closed for a period of time while the students were taken to another Washington County bus.
Fleming is charged with failure to control speed to avoid a collision.