A physics teacher at Animo Watts College Preparatory Academy asked his students to estimate the speed of a marble that was being blown out of a wooden and PVC pipe cannon, according to Los Angeles County Fire Department Inspector Scott Miller.
The cannon exploded at about 9:30 a.m., injuring 10 students, five of whom were taken to the hospital, Miller said. Five other students stayed with parents and may have been taken to hospitals by their families, Miller said.
"You could just hear a really loud, loud noise," student Carlos Ramirez said. "Everybody panicked; I don't know what happened. They called an emergency earthquake drill … and said everybody had to evacuate the school."
One person who came to the scene said her relative had been hit in the face and was bleeding.
The school, in the 12600 block of South Avalon Boulevard, was partly evacuated and students were standing on ball fields next to the campus.
The school is chartered by the Los Angeles Unified School District and is operated by Green Dot Public Schools.