About 40 students were aboard the bus at 8:30 a.m. when it crashed.
The California Highway Patrol said at least 16 students were taken to hospitals with what appeared to be minor injuries. Medical personnel were examining other students at the scene. It did not appear that any of the students were seriously injured.
The cause of the accident was under investigation.
Investigators told reporters at the scene that the bus driver braked suddenly. The driver may have been cut off by another vehicle or have come upon slow-moving traffic. The bus apparently overturned as it veered slightly off the roadway.
The students attend Preuss Charter, a middle and high school based at the University of California, San Diego. The accident partially blocked northbound lanes of Interstate Five and traffic backed up for several miles.
