The stabbing happened before 10:00 this morning as students were wrapping up the emergency exercise at a park next-door to Los Banos Junior High School.
Officials tell us it was the first time the campus held the drill at Talbott Park.
Because of its large student population, students were split into two different locations and about 500 kids were at the park when a 14-year-old student attacked another with a knife.
The victim was airlifted to UC Davis Medical Center with several stab wounds to his arms and torso, and underwent surgery Thursday afternoon.
Officials tell us several teachers chased down the suspect and he was taken into custody several blocks away.
Watch the video for extended coverage from Action News reporter Linda Mumma.