Guided meditation
This is specially designed for teenagers. Sitting Still application is a accessible and pleasant tool for winding down your overloaded brain. This application is paid app and it has 72MB size. Here are some feature of this app that you need to check once :
Opt for a short or a long meditation.
Set your own meditation duration.
Keep notes to track your progress.
https://play.google.com/store/apps/details?id=com.sittingstill.app