High school students who started school at Kansas City’s Ewing Marion Kauffman School saw something new when they entered their classrooms: a cellphone lockbox.

A new policy requires all high school students to lock away their phones for the day. Students drop their mobiles into the box, which is designed for phones, and it’s locked into after school hours, said Deon Whitten, dean of students at the charter school. The restrictions were instituted after a pilot study in 2023 with one ninth grade class showed those phone-free students had the highest GPA across the school, said Whitten.

Once administrators saw the academic achievements the decision to restrict phones came easily. “There is a certain pressure with phones,” said Whitten, 39, who has been at the charter school for about three years. “Now they could go to school and just be students. They don’t have to worry.”

Teachers and administrators have long known cellphones were major distractions in learning: A 2023 Pew survey showed 72%  of high school teachers view cellphones as a major problem in their classrooms.

U.S. Surgeon General Dr. Vivek Murthy issued an advisory on the effects of social media on youth mental health. This week he also issued an advisory on “parental stress,” specifically naming monitoring children’s phone use as a cause.