Here are some apps you can explore to monitor your teen’s activity on a phone:
This allows you to set phone time limits and filter web content coming in.
This allows you to track your child’s calls, texts, GPS and social media activity.
This enables you to view your child’s website browsing and set time limits.
This enables you to do all of the above, but it is available for fewer devices.
This allows you to limit phone Internet use during family meals.
This allows you to track and set a phone curfew where phones shut down.
There are actually several other apps that empower a parent to know what’s happening on their child’s phone. While they are minors, I think you should know.
One other idea might be for parents encourage their children to use privacy settings to ensure their posts are going out to a select set of friends.