A woman who was lecturing high school boys on the perils of drunk-driving knew she had driven her message home when some teenagers in her audience began to blanche, buckle and heave.

More than a dozen boys at a Roman Catholic high school in Chicago fainted during a speech in which crash survivor Marti Belluschi described in grisly detail the injuries she suffered in the wreck and the facial reconstruction surgery she required afterwards, the Chicago Tribune reported.

Seven boys who felt faint and queasy were taken to hospital following the incident.

"I nearly vomited a few times listening to her," said Danny Bowery, 14, who returned to school after being checked out in hospital.

"Definitely, I got her message."

"They were dropping like flies in the gym," Brother Konrad Diebold, president of St Patrick High School, said.

"I saw one of them throwing up in a bucket."