OCEANSIDE, Calif.—On a Monday morning last month, highway patrol officers visited 20 classrooms at El Camino High School to announce some horrible news: Several students had been killed in car wrecks over the weekend.

Classmates wept. Some became hysterical.

A few hours and many tears later, though, the pain turned to fury when the teenagers learned that it was all a hoax — a scared-straight exercise designed by school officials to dramatize the consequences of drinking and driving.

As seniors prepare for graduation parties Friday, school officials in the largely prosperous San Diego suburb are defending themselves against allegations they went too far.

At school assemblies, some students held up posters that read: “Death is real. Don’t play with our emotions.”

Michelle de Gracia, 16, was in physics class when an officer announced that her missing classmate David, a popular basketball player, had died instantly after being rear-ended by a drunken driver. She said she felt nauseated but was too stunned to cry.

“They got the shock they wanted,” she said.

Some of her classmates became extremely upset, prompting the teacher to tell them immediately it was all staged.

“People started yelling at the teacher,” she said. “It was pretty hectic.”

Others, including many who heard the news of the 26 deaths between classes, were left in the dark until the missing students reappeared hours later.

Officials at the 3,100-student school officials defended the program.

“They were traumatized, but we wanted them to be traumatized,” said guidance counselor Lori Tauber, who helped organize the shocking exercise and got dozens of students to participate. “That’s how they get the message.”