Teens say it’s easier to buy marijuana than cigarettes or beer, according to a new survey.

One-third of teens polled by the National Center on Addiction and Substance Abuse said they could buy the drug in just a few hours. More than one-fourth say it would take them an hour or less.

It’s the first time since the study began in 1996 that marijuana has edged out cigarettes and beer as the easiest drug for teens to buy. But 75 percent of students said they’ve never smoked it.

One in 12 said there’s a teacher at their school who uses illegal drugs.

The survey doesn’t specify whether it’s easy for kids to buy drugs at school. More than 60 percent say their schools are “drug-free” — the first time in the survey’s seven-year history that a majority of public school students are reporting drug-free schools. But one-fourth say they’ve seen illegal drugs being sold at school.

“The dramatic increase in the number of drug-free schools demonstrates that change is possible,” said Joseph Califano Jr., CASA president. “Yet too many parents remain silent while their teens continue to be put at risk by attending drug-infested schools.

“It’s time all American parents get as angry about drugs in schools as they are about asbestos in schools,” he said.

The survey also analyzed a sibling’s role on a teen’s substance-abuse risk. According to the survey, 67 percent of teens with an older sibling said their older brothers or sisters would be “very angry” to find out they were using marijuana. These teens are at a substantially lower risk of substance abuse.

However, 48 percent of teens with an older sibling believe that sibling may have tried illegal drugs. These younger teens are 1.5 times likelier to smoke, drink or use illegal drugs than the average teen. And 12 percent of teens with an older sibling reported that an older brother or sister had offered them illegal drugs or encouraged their use — which increases the younger sibling’s risk of substance abuse to two times that of other teens.

A Houston principal said drug prevention programs and random locker and backpack searches send a clear message that schools “take a real hard line on drugs.”