The incident occurred Aug. 27, with parents previously only knowing that a student was injured and not shot. Police believe the bullet was likely fired from off-campus and are still searching for the shooter.
A letter from the school's principal Elsa Bolado was sent to parents Tuesday night notifying them of the boy being shot.
"We have received further information that the injury appears to be a result of an "off-campus" discharge of a firearm from an unknown location or person, whereby the projectile came to rest within the campus perimeter, striking a student," said Bolado's message.
The student is recovering and expected to be OK.
Los Angeles Unified School District said it was cooperating with LAPD in the investigation.