Updated: 12 September 2022
If the child is under 13, they won’t be able to reset their password if they’ve forgotten it. That’s because we don’t ask for their email address when they register, so we can't send them a password-reset email. You, as the parent or guardian may have helped with creating the password, so you might be able to remember it.
If neither of you can remember the password you'll need to register a new child account.
Wondering why we don't ask children under 13 for their email? It's because we take their privacy very seriously, so we don't ask them for an email address.