Hi JenniferRoss84,
To clarify, on your child's iPhone Face ID & Passcode no longer show under Settings?
If you've disabled the parental controls, was there also a profile installed to this iPhone?
Install or remove configuration profiles on iPhone
Configuration profiles define settings for using iPhone with corporate or school networks or accounts. You might be asked to install a configuration profile that was sent to you in an email, or one that is downloaded from a webpage. You’re asked for permission to install the profile and, when you open the file, information about what it contains is displayed. You can see the profiles you have installed in Settings
> General > Profiles & Device Management. If you delete a profile, all of the settings, apps, and data associated with the profile are also deleted.
If a profile is installed, it's likely the cause of Face ID and Passcode not showing as an option. If you don't know where it came from, feel free to remove it. If it was placed there by a school or administrator, you may need to reach out to them to tweak or remove it.
Cheers!