Contact record ownership for self-registration
Who is the owner for Contact records if the Contact is created through self-registration?
When self-registration is enabled for a digital experience site and the "default" account is set, the contact created via the self-registration process will be parked under the "default" account and owned by the same owner.
For any custom development with self-registration, it is recommended to set the "default" owner. When a contact record is created via the self-registration, we could have the custom trigger on the Contact object to unset the AccountId field to force the EDA automation to create an administrative account for the student contact.
Please contact firstname.lastname@example.org and mention this article to get some sample codes for the trigger.