Here's how to disable Private DNS on your child's Android.
Samsung
On your kid's Samsung, open Settings.
Tap Connections.
Tap More connection settings.
Turn off Private DNS.
Other Androids
On your kid's Android, open Settings.
Tap Network.
Tap Advanced.
Turn off Private DNS.
Don't want to do this?
Consider the Bark Phone! It automatically locks down Private DNS along with other tamper-proof settings.