G'day BoogzfromOC,
Thanks for reaching out. We'd like to see if we can assist. To double-check, is he using his own Apple ID, or is he using yours?
If he's using your Apple ID on the device and you have it set to require a password for all purchases, it might be good to change the Apple ID password. Here's how: Change your Apple ID password - Apple Support
As another possibility, if you're using Family Sharing and he has his own Apple ID, you could try using Ask to Buy, which requires you to authorize any purchases. See this link for more detail: Approve what kids buy with Ask to Buy - Apple Support
If you already have Ask to Buy turned on, this link has some suggestions that could be helpful as well: If Ask to Buy isn't working - Apple Support
Let us know how it goes. Take care.