In Colorado, students are reportedly finding a new way to smoke pot in the classroom without their teachers knowing.

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Here's more from CBS Denver:

Students are using vapor pens, and they’re using them in classrooms. It’s becoming a problem at Lakewood High School.

“I’ve seen people in my math class and they’ll be sitting there with the teacher and they’ll be smoking it and they won’t even know,” said Jack Maestas, a student at Lakewood High.

Principal Ron Castagna has good things to say about his student body, but he’s not happy to see vapor pens in his school. Staff at Lakewood High know the gestures of vapor pen use.

“Teachers are aware of what to look for. The nervous habit of biting on your pen has a new meaning to it,” Castagna said.

Vapor pen are just like e-cigarettes. The can be purchased at grocery stores for $25.00 and up. When used for marijuana there’s no “skunk” smell, which makes it easy for students to bring them to school.