The average American teen spends about nine hours a day on entertainment media, according to a new report by Common Sense Media. That’s screen time on TVs, phones, tablets and computers, and doesn’t include similar activities at school. 

“Teens spend far more time with media and technology than they do in school, or with their parents, or even sleeping,” said James Steyer, CEO of Common Sense Media. Steyer —and child psychologists — are worried about all that exposure to commercial content during all that screen time.

But the knowledge that the young and impressionable demographic is consuming so much content can be useful information for companies.

“There are clearly business opportunities when the average teenager is spending nine hours a day using media and technology,” Steyer said, “and I think the companies recognize that. But at the same time, they have a much greater responsibility than they’ve demonstrated to date, to take action around this.”

Companies argue they are reaching their customers where they are, and that younger audiences are often voluntarily engaging with their favorite brands.  

“The fact is is that this amount of time is going to be spent on their screens probably regardless of what brands do,” said MaryLeigh Bliss of Ypulse, a market research firm focused on teens and millennials.

The Common Sense media survey also found that many of a teen’s media hours are spent multitasking—doing homework while Snapchatting, for example. This matches with what Bliss sees in her market research.

“[Teens] are very adept at looking at multiple screens and multiple kinds of media at once. So it’s not necessarily a negative. It’s actually an opportunity for you to play into that kind of behavior,” she said, mentioning things like a TV show engaging with fans on Twitter as the show is airing.

But that opportunity for engagement comes with a cost, according to professor Mara Einstein of Queens College in New York.

“That constant moving from focusing on one piece of content to another piece of content  doesn’t give you the same sort of depth of understanding  that you would get if you just focused on one thing at a time,” Einstein said, regardless of whether that thing is an ad or a homework assignment.

She also said parents need to warn young people about advertising in unexpected places.

“If you let kids understand that most of this is trying to sell you something, they have a bias behind it, they’re trying to get your money,” Einstein said, “then they begin to look at content in a different way.”

She said most youth — and many adults — struggle to distinguish between ads and original content. And, sometimes, what’s interesting to teens can be both.