Happy April 20. For the uninitiated, April 20, or “four-twenty” in casual language, is the unofficial holiday of marijuana users. With the drug in the news, let’s use the opportunity to look at data on marijuana in schools.

According to a 2013 Centers for Disease Control and Prevention survey, about one in four high schoolers reported using marijuana in the last 30 days. That’s not much different than the number from 2011, but it is up from roughly one in five high schoolers in 1993.