This is found in security just below the Account PIN controls and once turned on disables all chat functionality in the game and limits the games that they can play to only those that Roblox has ...

Finally, Roblox is introducing accounts with parent privileges. The current system is tied to parent’s email accounts and allow them to set a PIN and get notifications.

Learn how to set up a Roblox account, where to find stuff in the app, what types of games you can play, and what exactly Robux are.