Students at a pair of area high schools were given a sobering reminder Friday of the extreme dangers associated with driving under the influence. They watched as classmates were torn from mangled vehicles and lifted from the ground, their scarred and lifeless faces covered with white sheets, and placed in ambulances and even a coroner’s van. Rows of young people looked on as police and fire personnel surrounded the scene of a three-car accident, bandaging survivors and preparing for transport those who were not so lucky.