A new back-to-school survey found that many teenagers are drinking, doing drugs or smoking cigarettes during the school day.

According to Columbia University's National Center on Addiction and Drug Abuse, nearly nine out of 10 high school students reported some of their peers are taking part in the illicit behavior while at school.

The survey also found that almost half of the students know a fellow teen selling drugs on campus. For private schools, more than half of students said drugs are prevalent on school grounds.