Screen time reset by child

My child has an iPhone and an iPad. I setup screen time using my family parent account. I can see screen time is turned on for childs devices.

The screen time passcode resets every day to 0000. For example, I set a code of 3050 and then later it reset to 0000. I think my child resets the passcode.

Passcode never turned off, but changed to 0000

I change their ApplelD password ,and don’t tell them

the new password, but still screen time passcode resets. I change my AppleID password, too.

I change the screen time passcode. I'm doing this every day. But still the passcode change happens after I change the passcode.

In screen time, I see them use Settings every day.

In Screen time, I disable to Content and Privacy Restrictions and disable Accounts.