This year, 21.4% of high school seniors said they had used marijuana in the last 30 days, while 19.2% reported smoking cigarettes in the same time period, according to the annual “Monitoring the Future” survey from the National Institute on Drug Abuse. It was the first time since 1981 that pot surpassed tobacco in that age group.

The remarkable crossover is a victory for public health campaigns aimed at stamping out cigarette smoking among teens. But the federal office that tracks illicit drug use said it was driven by an uptick in youth marijuana use that is broad-based and likely to continue, with even eighth-graders reporting softer attitudes about the risk of smoking pot.