About 17% of American high school students drink, smoke or use drugs during the school day, a new survey by the National Center on Addiction and Substance Abuse at Columbia University says.

It’s no surprise to their classmates, either: 86% say they know the 2.8 million who are abusing substances during the day, according to the latest version of the center’s annual back-to-school survey. The estimate is based on information gleaned from telephone interviews with about 1,000 kids ages 12 to 17.

The survey found that 44% of high school students know a classmate who sells drugs at school, and 60% say that drugs are available on campus. Marijuana was the most-sold on school grounds, students said, as well as prescription drugs, cocaine and ecstasy.

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