The accident happened just before 8 a.m. Wednesday on Highway 71 at Tucker Hill Lane.
Surveillance video from a gas station in the area shows the bus getting hit by an 18-wheeler.
The truck driver said he had a yellow light, but the video shows the bus had the green light.
A witness went to help the truck driver, who said he did try to stop.
Bastrop ISD says 19 students headed to high school and middle school were on the bus at the time. Eight students were taken to a hospital by ambulance, and two others were taken by their parents.
The bus driver was also taken to a hospital for treatment.
The extent of the injuries is unknown at this time.
The accident remains under investigation.