Officers responded to the school at 1050 Neroly Road around 11:30 a.m. after receiving reports that a female student had been injured by another girl on campus, Oakley police Chief Bani Kollo said.
The victim, who suffered possible head injuries, was airlifted to John Muir Medical Center.
Kollo said police arrested the other student involved in the altercation on suspicion of felony battery. That student's name was not released, since she is a juvenile.
The chief said investigators are continuing to conduct interviews and have not determined whether the two girls were engaged in a mutual fight or how many people participated.
Police are still investigating what prompted the incident.
