I don't think this is possible.
Also, this doesn't exactly answer your question, but my children know that changing the passcode to their devices without permission will result in immediate suspension of their access to said device.
I think a practical answer has been given by the above posters. Either add your fingerprint, or face ID profile, depending on which model phone.
This won't help for when the phone is restarted, but will allow you access the majority of the time.