phone shadowing

Get him an "Old School" flip phone. He can make calls and basic texting.

You can't. Apple's security model does not make exceptions for "good causes" because it would be too easily abused by "bad guys".

There are some things you can do, however:

• You can set up Family Sharing (Family Sharing - Apple Support) and, if he is under 18, you can require that you approve any apps that he wants to download.
• You can set a restriction to prevent him from downloading any apps at all.
• You can also set restrictions on the types of sites he can visit.
• But you can't see his text messages, except by looking at them on his phone. With iOS 12.1 you can assign a passcode to unlock his phone and prevent him from changing it, so any time you have physical possession of his phone you can see what is on it.
• There IS one way to see his texts, but it would require you to have a 2nd phone just for this purpose. You log it in to his iCloud account, turn on iCloud text syncing; then all of his texts will be echoed on the 2nd phone. You don't want to do this with a phone you use for anything else, however, because he can also see what is being done on that phone.
• You can manage and review his screen time on your phone, also with iOS 12.1.
• See: Use parental controls on your child's iPhone, iPad, and iPod touch - Apple Support for all of the parental control features that are available for your use.