The survey released by Partnership for a Drug-Free America and MetLife Foundation indicates that among parents who drank or used drugs at their prom, 66 percent set a "zero tolerance policy" for their teens. Among parents who did not use alcohol or drugs at their prom, 87 percent set hard rules about drinking and drugs for their children.

Fifty-one percent of parents who used drugs or alcohol are more likely to suspect that teens will as well, vs. 36 percent of parents who didn't use drugs or alcohol.

Sixteen percent of teens whose parents set a zero tolerance policy for drugs and alcohol reported they were likely to use drugs or alcohol, while 45 percent of teens whose parents didn't set such boundaries reported they were likely to drink or use drugs at a prom or graduation party this year.

The survey of 1,000 teens in grades nine to 12 and 1,003 parents, conducted by Kelton Research, has a margin of error of 3.1 percent.