Schools should perform random security screenings, say safety experts.

Security officers wielding metal detecting wands meticulously searched students Wednesday as they waited in a long line outside a Los Angeles high school where two 15-year-olds were shot in a classroom a day earlier.

The stepped-up security measures come after a 9 mm semiautomatic handgun being carried in a backpack by a 10th-grader discharged Tuesday when he put the bag down on a desk at Gardena High School, authorities said.

A bullet pierced a boy in the neck, exited, and hit a girl in the head. The boy was doing well Wednesday, while the girl remained in serious condition with a skull fracture.

The girl regained consciousness and could move her body after surgery to remove a blood clot from her brain caused by the bullet’s impact, said Julie Rees, spokeswoman for Los Angeles County Harbor-UCLA Medical Center. The boy was expected to be discharged Wednesday night, Rees said.

The 17-year-old suspect, who was already on probation for a fight at school, was arrested. Police said two other students were also taken into custody for investigation of concealing evidence.

A boy traded clothes with the fleeing suspect, and a girl took the backpack, police Detective A. Batris said.

In an unrelated incident, authorities said a bulletproof vest saved the life of a Los Angeles school police officer who was shot Wednesday as he confronted a man who appeared to breaking into cars near El Camino Real High School in Woodland Hills. Police Chief Charlie Beck said the man got out of a car and fired several times, hitting the officer at least once in the chest. A manhunt was under way.

Also Wednesday, a 16-year-old boy was shot in a restaurant parking lot near his high school in the Los Angeles suburb of Bell, authorities said. The Bell High School student was shot once in the abdomen, but his vital signs appeared good when he was taken to a hospital, Bell police Captain Anthony Miranda said.