A student who does not have a valid email address can sign up using a 'dummy' address.
The only drawback to using a dummy (fake) email address is the student will not receive any password reset emails, nor any class emails from the teacher. The teacher can reset the student's password from the Students page instead.
Create an account with a dummy email
The @edustile.com domain is owned by Stile and available for students to create dummy accounts. It can not send/receive emails and does not provide the user with an email inbox.
Some suggestions for naming schemes on the dummy email include:
The student must sign up using a class code because the email address will not receive an invitation email.
Add a digit to the end of the student's name if the email address is already taken (for example: firstname.lastname@example.org).
You may also be interested in the following resources: