Unknown gunmen, who are still at large, opened fire on the students at their school's parking lot.
It was reported that the victims, three male and one female are students of the San Francisco Unified School District, and were shot outside their school building.
"This was an isolated incident outside of the school building where one student was being targeted by outsiders," the school district said.
According to Officer Carlos Manfredi who spoke to CNN, the students were shot at the high school parking lot and ran to the school for safety.
The 15-year-old female victim in critical condition was taken to San Francisco General Hospital for treatment, report said.
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The other victims - two of them are being hospitalised while the third walked into the San Francisco Police Department with minor injuries, Police said.
Police are after four suspects in connection to the shooting.