Two 17-year-olds were arrested and weapons were seized after the boys were overheard talking about a "hit list".
The boys were detained at their homes in Twentynine Palms, a desert community some 140 kilometers (90 miles) east of Los Angeles, police said.
Sheriffs' deputies also searched both boys' homes, and found a .22-caliber rifle in one home, and in the other a list of 16 names of students who were allegedly to be targeted.
San Bernadino County police were told yesterday that the boys - whose names were not released - were overheard in recent weeks talking about killing fellow students at Monument High School.
News of the arrest came two days after a student at a San Diego-area high school murdered two classmates and wounded 13 others, and the same day a girl was wounded in a shooting at a Roman Catholic high school in Williamsport, Pennsylvania.
A female suspect was in custody in that incident, police said.
AFP