Is your teen struggling at school?

Their smartphone could be dividing their attention in class, a new study says.

Teenagers average more than 70 minutes a day on their smartphones during school hours, researchers reported Jan. 5 in the Journal of the American Medical Association.

“We found that teens spent more than an hour on their phones during the school day on average, largely on social media, video and gaming apps,” said lead researcher Dr. Jason Nagata, a professor of pediatrics at the University of California-San Francisco.

“That time inevitably competes with attention to learning,” he added in a news release.

For the study, researchers analyzed data from 640 13- to 18-year-olds participating in a long-term research project on brain development. As part of the project, their smartphone use was measured using a tracking app installed on their phone.

"This moves the conversation beyond anecdotes and self-reports to real-world behavior,” Nagata said. “Teens are not always accurate reporters of their own screen time. Objective smartphone data gives us a clearer picture of actual use."

Social media apps like Instagram, TikTok and Snapchat accounted for the greatest share of smartphone use during school hours, researchers said. Teens spent nearly 30 minutes a day on those apps alone.

Video-streaming apps and video games followed at nearly 15 minutes each.

Nearly all U.S. public schools have policies intended to limit screen time during the school day, but these findings show that smartphone use still takes up a sizable portion of students’ time, researchers said.

“Many school policies assume phones are largely out of sight during the day,” Nagata said. “But objective data show that smartphones remain a significant part of students’ school-day experience.”

In particular, Black teenagers tend to sneak more smartphone peeks during the school day, researchers said. Data show Black students spent 12 to 20 additional minutes per day on smartphones during school hours, compared to their white classmates.

Teenagers from lower-income homes also racked up more smartphone minutes during school, researchers said.

"School phone policies are changing rapidly, but until now we have had very little objective data on what students actually do with their phones during the school day,” Nagata said.

"Smartphones can support learning and connection, but without clear boundaries they can also be a constant distraction,” he concluded.