Deniz, 17, was in the first year of secondary school when she got a smartphone after she began walking to school by herself.
She is now in her final year of sixth form at The Duston School, Northampton, and said she used her phone mostly for social media.
Deniz estimated she spent about four hours a day on her phone during the week – but the figure goes up at weekends and during half-term.
Students at The Duston School are allowed a limited access to their phones.
She said she has mixed feelings about the policy as “it definitely has its benefits and drawbacks”.
“The benefits are you can access work that’s been set if the computers are all full, but the drawbacks are you can get carried away and just start scrolling,” she said.