According to KIDslox the average teen spends about 9 hours a day looking at their mobile devices.

If you need help controlling your child’s screen time KIDslox parental control app can help.Install the app on the parent’s device, as well as, your child’s phone or tablet.  On your child’s device you can set restrictions like blocking individual apps and inappropriate content.  You can also set limits to manage the amount of time spent on a device each day.  Under schedules: set bed times, homework and dinner times to put the phone on lockdown during those hours. KIDslox is full featured with a great user interface.  It offers a 14-day free trial and then its $3.99 per month