SAN ANTONIO –Professional basketball trainer David Jones is just as worried about his students off the court as he is on the court with a popular, but troubling vaping trend.

"They say have you heard of it? Oh it's really cool, oh one of my classmates, he does it. When I hear about it, I get our kids in a group and talk to them about what's right and what's wrong," said Jones.

Many know it as e-cigarettes, or vaping, but to students it is better known as Juuling - after the vaporizer brand, Juul.

More and more middle and high school students are vaping. A 2016 report by the US surgeon general cited a 900 percent increase in e-cigarette use by high school students from 2011 to 2015.

In this circle of San Antonio students, about half, some as young as 11 years old, know someone who has vaped.

"We sat down with Caden and asked him if some of his friends do it and he indicated that some of his friends do," said parent Adrian Wong.

"It's kinda easy, you can smell it in the bathroom. Some kids actually do it like in our class," said student Caden Wong.

It is so easy because the vaporizers aren't always easy to spot. Some look like a USB flash drive. Just this month, administrators at Reagan High School sent letters home to parents, warning them about the trend.

"I don't want my kid starting up a habit," said Wong.

Many people think vaping is safer than smoking, and vaporizers come in flavors like cotton candy. However, many vape juices still contain nicotine. Some studies have found the liquid also contains chromium and lead.

"That's the really scary part. You can get sucked in by what you think it may be but it's really not," said Jones.

For now, parents said they can only talk to their kids.

"We try to have an open dialogue with all of our kids and the biggest things is to let them know the reason why that we think it's not healthy," said parent Michael Maloy.

They hope their children take the advice.